[ { "text": "Neutral weak currents in nucleon superfluid Fermi liquids: Larkin-Migdal\n and Leggett approaches: Neutrino emission in processes of breaking and formation of nucleon Cooper\npairs is calculated in the framework of the Larkin-Migdal and the Leggett\napproaches to the description of superfluid Fermi liquids at finite\ntemperatures. We explain peculiarities of both approaches and explicitly\ndemonstrate that they lead to the same expression for the emissivity in pair\nbreaking and formation processes.", "category": "nucl-th" }, { "text": "Fragments in Gaussian Wave-Packet Dynamics with and without correlations: Generalization of Gaussian trial wave functions in quantum molecular dynamics\nmodels is introduced, which allows for long-range correlations characteristic\nfor composite nuclear fragments. We demonstrate a significant improvement in\nthe description of light fragments with correlations. Utilizing either type of\nGaussian wave functions, with or without correlations, however, we find that we\ncannot describe fragment formation in a dynamic situation. Composite fragments\nare only produced in simulations if they are present as clusters in the\nsubstructure of original nuclei. The difficulty is traced to the delocalization\nof wave functions during emission. Composite fragments are produced abundantly\nin the Gaussian molecular dynamics in the limit $\\hbar \\rightarrow 0$.", "category": "nucl-th" }, { "text": "Multi-nucleon structure and dynamics via quantum computing: We propose a framework for computing the structure and dynamics for\nsecond-quantized many-nucleon Hamiltonians on quantum computers. We develop an\noracle-based Hamiltonian input model that computes the many-nucleon states and\nnonzero Hamiltonian matrix elements of the many-nucleon system. With our\nFock-state based input model, we show how to implement the sparse matrix\nsimulation algorithms to calculate the dynamics of the second-quantized\nmany-nucleon Hamiltonian. Based on the dynamics simulation methods, we also\npresent the methodology for structure calculations of the many-nucleon system.\nIn this work, we provide an explicit circuit design of our input model of the\nsecond-quantized Hamiltonian within a direct encoding scheme that maps the\noccupation of each available single-particle state in the many-nucleon state to\nthe state of specific qubit in a quantum register. We analyze our method and\nprovide the asymptotic cost in computing resources for structure and dynamics\ncalculations of many-nucleon systems. For pedagogical purposes, we demonstrate\nour input model with two model problems in restricted model spaces.", "category": "nucl-th" }, { "text": "Aspects of Hadron Physics: Detailed investigations of the structure of hadrons are essential for\nunderstanding how matter is constructed from the quarks and gluons of Quantum\nchromodynamics (QCD), and amongst the questions posed to modern hadron physics,\nthree stand out. What is the rigorous, quantitative mechanism responsible for\nconfinement? What is the connection between confinement and dynamical chiral\nsymmetry breaking? And are these phenomena together sufficient to explain the\norigin of more than 98% of the mass of the observable universe? Such questions\nmay only be answered using the full machinery of nonperturbative relativistic\nquantum field theory. This contribution provides a perspective on progress\ntoward answering these key questions. In so doing it will provide an overview\nof the contemporary application of Dyson-Schwinger equations in Hadron Physics.\nThe presentation assumes that the reader is familiar with the concepts and\nnotation of relativistic quantum mechanics, with the functional integral\nformulation of quantum field theory and with regularisation and renormalisation\nin its perturbative formulation.", "category": "nucl-th" }, { "text": "Nucleon resonances within a dynamical coupled-channels model of pi N and\n gamma N reactions: The nucleon resonances are investigated within a dynamical coupled-channels\nmodel of pi N and gamma N reactions up to the invariant mass W = 2 GeV. The\nmeson-baryon (MB) channels included in the calculations are MB = pi N, eta N, K\nLambda, K Sigma, and pi pi N that has pi Delta, rho N, and sigma N resonant\ncomponents. The meson-baryon amplitudes T_{M'B',MB}(W) are calculated from\nsolving a set of coupled-channels integral equations defined by an interaction\nHamiltonian consisting of (a) meson-exchange interactions v_{M'B',MB} derived\nfrom phenomenological Lagrangian, and (b) vertex interactions N* --> MB for\ndescribing the transition of a bare excited nucleon state N* to a channel MB.\nThe parameters of v_{M'B',MB} are mainly constrained by the fit to the data of\npi N --> pi N in the low energy region up to W =1.4 GeV. The bare masses of N*\nand the N* --> MB parameters are then determined in simultaneous fits to the\ndata of pi N --> pi N up to W =2.3 GeV and those of pi N --> eta N, K Lambda, K\nSigma and gamma N --> pi N, eta N, K Lambda, K Sigma up to W = 2.1 GeV. The\npole positions and residues of nucleon resonances are extracted by analytically\ncontinuing the meson-baryon amplitudes T_{M'B',MB}(W) to the complex Riemann\nenergy surface. From the extracted residues, we have determined the N* --> pi\nN, gamma N, eta N, K Lambda, K Sigma transition amplitudes at resonance poles.\nWe compare the resonance pole positions from our analysis with those given by\nParticle Data Group and the recent coupled-channels analyses by the Juelich and\nBonn-Gatchina groups. Four results agree well only for the first N* in each\nspin-parity-isospin (J^P,I) channel. For higher mass states, the number of\nstates and their resonance positions from four results do not agree well. We\ndiscuss the possible sources of the discrepancies and the need of additional\ndata from new hadron facilities such as J-PARC.", "category": "nucl-th" }, { "text": "Bose-Einstein correlations in thermal field theory: Two-particle correlation functions are calculated for bosons emitted from a\nlocalized thermal source (the ``glow'' of a ``hot spot''). In contrast to\nexisting work, non-equilibrium effects up to first order in gradients of the\nparticle distribution function are taken into account. The spectral width of\nthe bosons is shown to be an important quantity: If it is too small, they do\nnot equilibrate locally and therefore strongly increase the measured\ncorrelation radius. In memoriam of Eugene Wigner and Hiroomi Umezawa.", "category": "nucl-th" }, { "text": "Spin and pseudospin symmetries in the antinucleon spectrum of nuclei: Spin and pseudospin symmetries in the spectra of nucleons and antinucleons\nare studied in a relativistic mean-field theory with scalar and vector\nWoods-Saxon potentials, in which the strength of the latter is allowed to\nchange. We observe that, for nucleons and antinucleons, the spin symmetry is of\nperturbative nature and it is almost an exact symmetry in the physical region\nfor antinucleons. The opposite situation is found in the pseudospin symmetry\ncase, which is better realized for nucleons than for antinucleons, but is of\ndynamical nature and cannot be viewed in a perturbative way both for nucleons\nand antinucleons. This is shown by computing the spin-orbit and\npseudospin-orbit couplings for selected spin and pseudospin partners in both\nspectra.", "category": "nucl-th" }, { "text": "Isovector giant monopole and quadrupole resonances in a Skyrme energy\n density functional approach with axial symmetry: [Background] Giant resonance (GR) is a typical collective mode of vibration.\nThe deformation splitting of the isovector (IV) giant dipole resonance is well\nestablished. However, the splitting of GRs with other multipolarities is not\nwell understood. [Purpose] I explore the IV monopole and quadrupole excitations\nand attempt to obtain the generic features of IV giant resonances in deformed\nnuclei by investigating the neutral and charge-exchange channels\nsimultaneously. [Method] I employ a nuclear energy-density functional (EDF)\nmethod: the Skyrme-Kohn-Sham-Bogoliubov and the quasiparticle random-phase\napproximation are used to describe the ground state and the transition to\nexcited states. [Results] I find the concentration of the monopole strengths in\nthe energy region of the isobaric analog or Gamow-Teller resonance irrespective\nof nuclear deformation, and the appearance of a high-energy giant resonance\ncomposed of the particle-hole configurations of $2\\hbar \\omega_0$ excitation.\nSplitting of the distribution of the strength occurs in the giant monopole and\nquadrupole resonances due to deformation. The lower $K$ states of quadrupole\nresonances appear lower in energy and possess the enhanced strengths in the\nprolate configuration, and vice versa in the oblate configuration, while the\nenergy ordering depending on $K$ is not clear for the $J=1$ and $J=2$\nspin-quadrupole resonances. [Conclusions] The deformation splitting occurs\ngenerously in the giant monopole and quadrupole resonances. The $K$-dependence\nof the quadrupole transition strengths is largely understood by the anisotropy\nof density distribution.", "category": "nucl-th" }, { "text": "Low Energy Pion-Nucleus Interactions: Nuclear Deep Inelastic Scattering,\n Drell-Yan and Missing Pions: The experimental discovery that the nucleus is approximately transparent to\nlow energy pions is reviewed. The consequences of this for nuclear deep\ninelastic scattering and Drell-Yan interactions are discussed. I argue that low\nenergy nucleus data imply that there is little nuclear enhancement of the pion\ncloud of a nucleon, and try to interpret this in terms of nucleon-nucleon\ncorrelations.", "category": "nucl-th" }, { "text": "Light Front Theory Of Nuclear Matter: A relativistic light front formulation of nuclear dynamics is applied to\ninfinite nuclear matter. A hadronic meson-baryon Lagrangian, consistent with\nchiral symmetry, leads to a nuclear eigenvalue problem which is solved,\nincluding nucleon-nucleon (NN) correlations, in the one-boson-exchange\napproximation for the NN potential. The nuclear matter saturation properties\nare reasonably well reproduced, with a compression modulus of 180 MeV. We find\nthat there are about 0.05 excess pions per nucleon.", "category": "nucl-th" }, { "text": "Structure analysis of the virtual Compton scattering amplitude at low\n energies: We analyze virtual Compton scattering off the nucleon at low energies in a\ncovariant, model-independent formalism.\n We define a set of invariant functions which, once the irregular nucleon pole\nterms have been subtracted in a gauge-invariant fashion, is free of poles and\nkinematical zeros.\n The covariant treatment naturally allows one to implement the constraints due\nto Lorentz and gauge invariance, crossing symmetry, and the discrete\nsymmetries.\n In particular, when applied to the $ep\\to e'p'\\gamma$ reaction,\ncharge-conjugation symmetry in combination with nucleon crossing generates four\nrelations among the ten originally proposed generalized polarizabilities of the\nnucleon.", "category": "nucl-th" }, { "text": "Charged-particle rapidity density in Au+Au collisions in a quark\n combination model: Rapidity/seudorapidity densities for charged particles and their centrality,\nrapidity and energy dependence in Au+Au collisions at RHIC are studied in a\nquark combination model. Using a Gaussian-type rapidity distribution for\nconstituent quarks as a result of Landau hydrodynamic evolution, the data at\n$\\sqrt{s_{NN}}=130, 200$ GeV at various centralities in full pseudorapidity\nrange are well described, and the charged particle multiplicity are reproduced\nas functions of the number of participants. The energy dependence of the shape\nof the $dN_{ch}/d\\eta$ distribution is also described at various collision\nenergies $\\sqrt{s_{NN}}=200, 130, 62.4$ GeV in central collisions with same\nvalue of parameters except 19.6 GeV. The calculated rapidity distributions and\nyields for the charged pions and kaons in central Au+Au collisions at\n$\\sqrt{s_{NN}}=200$ GeV are compared with experimental data of the BRAHMS\nCollaboration.", "category": "nucl-th" }, { "text": "Meson Photoproductions of Nucleon In the Quark Model: The meson photoproductions off nucleons in the chiral quark model are\ndescribed. The role of the S-wave resonances in the second resonance region is\ndiscussed, and it is particularly important for the Kaon, $\\eta$ and $\\eta'$\nphotoproductions.", "category": "nucl-th" }, { "text": "Single- & double-strangeness hypernuclei up to $ A=8 $ within chiral\n effective field theory: We investigate $S=-1$ and $-2$ hypernuclei with $A=4-8$ employing the\nJacobi-NCSM approach and in combination with baryon-baryon interactions derived\nwithin the frame work of chiral effective field theory. The employed\ninteractions are transformed using the similarity renormalization group (SRG)\nso that the low- and high-momentum states are decoupled, and,\nthereby,convergence of the binding energies with respect to model space can be\nsignificantly speeded up. Such an evolution is however only approximately\nunitary when the so-called SRG induced higher-body forces are omitted. We first\nexplore the impact of the SRG evolution on the $\\Lambda$ separation energies\n$B_{\\Lambda}$ in $A=3-5$ hypernuclei when only SRG-evolved two-body and when\nboth two- and three-body forces are included. For the latter scenario, we\nthoroughly study predictions of the two almost phase-equivalent NLO13 and NLO19\nYN potentials for $A=4-7$ hypernuclei. The NLO19 interaction yields separation\nenergies that are comparable with experiment, whereas NLO13 underestimates all\nthe systems considered. We further explore CSB splittings in the $A=7,8$\nmultiplets employing the two NLO YN potentials that include also the leading\nCSB potential in the $\\Lambda$N channel, whose strength has been fitted to the\npresently established CSB in $A=4$. Finally, we report on our recent study for\n$\\Xi$ hypernuclei based on the $\\Xi$N interaction at NLO.", "category": "nucl-th" }, { "text": "Impact of Nucleon-Nucleon Bremsstrahlung Rates Beyond One-Pion Exchange: Neutrino-pair production and annihilation through nucleon-nucleon\nbremsstrahlung is included in current supernova simulations by rates that are\nbased on the one-pion-exchange approximation. Here we explore the consequences\nof bremsstrahlung rates based on a modern nuclear interactions for\nproto-neutron star cooling and the corresponding neutrino emission. We find\nthat despite a reduction of the bremsstrahlung emission by a factor of 2-5 in\nthe neutrinospheric region, models with the improved treatment exhibit only\n$\\lesssim$5% changes of the neutrino luminosities and an increase of\n$\\lesssim$0.7 MeV of the average energies of the radiated neutrino spectra,\nwith the largest effects for the antineutrinos of all flavors and at late\ntimes. Overall, the proto-neutron star cooling evolution is slowed down\nmodestly by $\\lesssim$0.5-1 s.", "category": "nucl-th" }, { "text": "System stability and truncation schemes to the Dyson-Schwinger Equations: With decades of years development, although important progresses have been\nmade by the pioneers of this field, providing a sophisticated truncation scheme\nis still a great challenge up to now if the Dyson-Schwinger Equations(DSEs) of\nboth quark and gluon propagators (or including even more DSEs) remain after\ntruncation. In this work we view the coupled reminiscent DSEs of the gluon and\nquark propagators after truncation as a system with feedback. Then studying the\nstability of this equation array gives useful results. Our calculation shows\nthat the sum of the gluon and ghost loops plays the most important role in\nkeeping this system stable and having reasonable solutions. The quark-gluon\nvertex plays a relative smaller but also important role. Our method also could\ngive constraints and inspirations on fabricating a more sophisticated model of\nthe quark-gluon vertex.", "category": "nucl-th" }, { "text": "Shape phase mixing in critical point nuclei: Spectral properties of nuclei near the critical point of the quantum phase\ntransition between spherical and axially symmetric shapes are studied in a\nhybrid collective model which combines the $\\gamma$-stable and $\\gamma$-rigid\ncollective conditions through a rigidity parameter. The model in the lower and\nupper limits of the rigidity parameter recovers the X(5) and X(3) solutions\nrespectively, while in the equally mixed case it corresponds to the X(4)\ncritical point symmetry. Numerical applications of the model on nuclei from\nregions known for critical behavior reveal a sizable shape phase mixing and its\nevolution with neutron or proton numbers. The model also enables a better\ndescription of energy spectra and electromagnetic transitions for these nuclei.", "category": "nucl-th" }, { "text": "Influence of anisotropic $\u039b/\u03a3$ creation on the $\u039e^-$\n mutiplicity in subthreshold proton-nucleus collisions: We present an analysis of $\\Xi^-$ baryon production in subthreshold\nproton--nucleus ($p+A$) collisions in the framework of a BUU type transport\nmodel. We propose a new mechanism for $\\Xi$ production in the collision of a\nsecondary $\\Lambda$ or $\\Sigma$ hyperon and a nucleon from the target nucleus.\nWe find that the $\\Xi^-$ multiplicity in $p+A$ collisions is sensitive to the\nangular distribution of hyperon production in the primary $N+N$ collision.\nUsing reasonable assumptions on the unknown elementary cross sections we are\nable to reproduce the $\\Xi^-$ multiplicity and the $\\Xi^-/(\\Lambda+\\Sigma^0)$\nratio obtained in the HADES experiment in $p$+Nb collisions at $\\sqrt{s_{NN}} =\n$ 3.2 GeV energy.", "category": "nucl-th" }, { "text": "Influence of complete energy sorting on the characteristics of the\n odd-even effect in fission-fragment element distributions: The characteristics of the odd-even effect in fission-fragment Z\ndistributions are compared to a model based on statistical mechanics. Special\ncare is taken for using a consistent description for the influence of pairing\ncorrelations on the nuclear level density. The variation of the odd-even effect\nwith the mass of the fissioning nucleus and with fission asymmetry is explained\nby the important statistical weight of configurations where the light nascent\nfission fragment populates the lowest energy state of an even-even nucleus.\nThis implies that entropy drives excitation energy and unpaired nucleons\npredominantly to the heavy fragment. Therefore, within our model, the odd-even\neffect appears as an additional signature of the recently discovered\nenergy-sorting process in nuclear fission.", "category": "nucl-th" }, { "text": "Can only flavor-nonsinglet H dibaryons be stable against strong decays?: Using the QCD sum rule approach, we show that the flavor-nonsinglet $H$\ndibaryon states with J$^{\\pi} = 1^+$, J$^{\\pi} = 0^+$, I=1 (27plet) are nearly\ndegenerate with the J$^{\\pi} = 0^+$, I=0 singlet $H_0$ dibaryon, which has been\npredicted to be stable against strong decay, but has not been observed. Our\ncalculation, which does not require an instanton correction, suggests that the\n$H_0$ is slightly heavier than these flavor-nonsinglet $H$s over a wide range\nof the parameter space. If the singlet $H_0$ mass lies above the $\\Lambda\n\\Lambda$ threshold (2231~MeV), then the strong interaction breakup to $\\Lambda\n\\Lambda$ would produce a very broad resonance in the $\\Lambda \\Lambda$\ninvariant mass spectrum which would be very difficult to observe. On the other\nhand, if these flavor-nonsinglet J=0 and 1 $H$ dibaryons are also above the\n$\\Lambda \\Lambda$ threshold, but below the $\\Xi^0n$ breakup threshold (2254\nMeV), then because the direct, strong interaction decay to the $\\Lambda\n\\Lambda$ channel is forbidden, these flavor-nonsinglet states might be more\namenable to experimental observation. The present results allow a possible\nreconciliation between the reported observation of $\\Lambda \\Lambda$\nhypernuclei, which argue against a stable $H_0$, and the possible existence of\n$H$ dibaryons in general.", "category": "nucl-th" }, { "text": "Impact of the symmetry energy on the outer crust of non-accreting\n neutron stars: The composition and equation of state of the outer crust of non-accreting\nneutron stars is computed using accurate nuclear mass tables. The main goal of\nthe present study is to understand the impact of the symmetry energy on the\nstructure of the outer crust. First, a simple \"toy model\" is developed to\nillustrate the competition between the electronic density and the symmetry\nenergy. Then, realistic mass tables are used to show that models with a stiff\nsymmetry energy - those that generate large neutron skins for heavy nuclei -\npredict a sequence of nuclei that are more neutron-rich than their softer\ncounterparts. This result may be phrased in the form of a correlation: the\nlarger the neutron skin of 208Pb, the more exotic the composition of the outer\ncrust.", "category": "nucl-th" }, { "text": "From 0 to 5000 in $2\\times 10^{-24}$ seconds: Entropy production in\n relativistic heavy-ion collisions: We review what is known about the contributions to the final entropy from the\ndifferent stages of a relativistic nuclear collision, including recent results\non the decoherence entropy and the entropy produced during the hydrodynamic\nphase by viscous effects. We then present a general framework, based on the\nHusimi distribution function, for the calculation of entropy growth in quantum\nfield theories, which is applicable to the earliest (\"glasma\") phase of the\ncollision during which most of the entropy is generated. The entropy calculated\nfrom the Husimi distribution exhibits linear growth when the quantum field\ncontains unstable modes and is asymptotically equal to the Kolmogorov-Sina\\\"i\n(KS) entropy. We outline how the approach can be used to investigate the\nproblem of entropy production in a relativistic heavy-ion reaction from first\nprinciples.", "category": "nucl-th" }, { "text": "Estimates of dilepton spectra from open charm and bottom decays: The spectra of lepton pairs from correlated open charm and bottom decays in\nultrarelativistic heavy-ion collisions are calculated. Our approach includes\nenergy loss effects of the fast heavy quarks in deconfined matter which are\ndetermined by temperature and density of the expanding parton medium. We find a\nnoticeable suppression of the initial transverse momentum spectrum of heavy\nquarks due to the energy loss within the central rapidity covered by the PHENIX\ndetector system. As a result the dilepton yields from correlated decays of\nheavy quarks are in the same order of magnitude as the Drell-Yan signal.", "category": "nucl-th" }, { "text": "A dynamical, confining model and hot quark stars: We explore the consequences of an equation of state (EOS) obtained in a\nconfining Dyson-Schwinger equation model of QCD for the structure and stability\nof nonstrange quark stars at finite-T, and compare the results with those\nobtained using a bag-model EOS. Both models support a temperature profile that\nvaries over the star's volume and the consequences of this are model\nindependent. However, in our model the analogue of the bag pressure is\n(T,mu)-dependent, which is not the case in the bag model. This is a significant\nqualitative difference and comparing the results effects a primary goal of\nelucidating the sensitivity of quark star properties to the form of the EOS.", "category": "nucl-th" }, { "text": "The piNN system - recent progress: Recent progress towards an understanding of the piNN system within chiral\nperturbation theory is reported. The focus lies on an effective field theory\ncalculation and its comparison to phenomenological calculations for the\nreaction NN->d pi. In addition, the resulting absorptive and dispersive\ncorrections to the pi-d scattering length are discussed briefly.", "category": "nucl-th" }, { "text": "Sensitivity study of experimental measures for the nuclear liquid-gas\n phase transition in the statistical multifragmentation model: The experimental measures of the multiplicity derivatives, the moment\nparameters, the bimodal parameter, the fluctuation of maximum fragment charge\nnumber (NVZ), the Fisher exponent ($\\tau$) and Zipf's law parameter ($\\xi$),\nare examined to search for the liquid-gas phase transition in nuclear\nmultifragmention processes within the framework of the statistical\nmultifragmentation model (SMM). The sensitivities of these measures are\nstudied. All these measures predict a critical signature at or near to the\ncritical point both for the primary and secondary fragments. Among these\nmeasures, the total multiplicity derivative and the NVZ provide accurate\nmeasures for the critical point from the final cold fragments as well as the\nprimary fragments. The present study will provide a guide for future\nexperiments and analyses in the study of nuclear liquid-gas phase transition.", "category": "nucl-th" }, { "text": "The nuclear liquid-gas transition in QCD: We estimate the nuclear saturation density and the binding energy in a\nnuclear liquid from precision data on the coupling of the four-quark scattering\nvertex in the vector channel, computed within functional QCD. We show that this\ncoupling is directly related to the density-density potential and the latter is\nused for the estimates. In a first qualitative computation we find a saturation\ndensity of 0.2 fm${}^{-3}$ and an upper bound for the binding energy of 21.5\nMeV, in agreement with the empirical values of 0.16 fm${}^{-3}$ and 16 MeV,\nrespectively. We also use the scattering vertex for constructing an emergent\nlow-energy effective theory for the liquid gas transition from QCD correlation\nfunction, whose coupling parameters can be determined within QCD. As a first\nconsistency check of this construction we estimate the in-medium reduction of\nthe nucleon pole mass.", "category": "nucl-th" }, { "text": "CHIRAL SYMMETRY CONSTRAINTS ON THE $K^+$ INTERACTION WITH THE NUCLEAR\n PION CLOUD: The real part of the $K^{+}$ selfenergy for the interaction of the $K^{+}$\nwith the pion nuclear cloud is evaluated in lowest order of chiral perturbation\ntheory and is found to be exactly zero in symmetric nuclear matter. This\nremoves uncertainties in that quantity found in former phenomenological\nanalyses and is supported by present experimental data on $K^{+}$ nucleus\nscattering.", "category": "nucl-th" }, { "text": "Neutrino/antineutrino-$^{12}$C charged cross sections in the projected\n QRPA formalism: The $\\nu/\\bar{\\nu}-^{12}$C cross sections are evaluated in the projected\nquasiparticle random phase approximation (PQRPA). The cross section for $\\nu_e$\nas a function of the incident neutrino energy is compared with recent\ntheoretical calculations of more sophisticated models. The $\\bar{\\nu}-^{12}$C\ncross section is calculated for the first time with the PQRPA. The distribution\nof cross sections averaged with the Michel spectrum as well as with other\nestimated fluxes for future experiments is compared for both $\\nu_e$ and\n$\\bar{\\nu}_e$. Some astrophysical implications are addressed.", "category": "nucl-th" }, { "text": "Many-body nuclear Hamiltonian: Ab exitu approach: Fully-microscopic No-core Shell Model (NCSM) calculations of all stable $s$\nand $p$ shell nuclei are used to determine realistic $NN$ interaction JISP16\ndescribing not only the two-nucleon data but the binding energies and spectra\nof nuclei with $A\\leq 16$ as well. The JISP16 interaction, providing rapid\nconvergence of the NCSM calculations, is obtained in an {\\em ab exitu} approach\nby phase-equivalent transformations of the JISP6 $NN$ interaction.", "category": "nucl-th" }, { "text": "Multiplicities in Au-Au and Cu-Cu collisions at \\sqrt{s_{NN}} = 62.4 and\n 200 GeV: Likelihood ratio tests are performed for the hypothesis that charged-particle\nmultiplicities measured in Au-Au and Cu-Cu collisions at $\\sqrt{s_{NN}} = 62.4$\nand 200 GeV are distributed according to the negative binomial form. Results\nsuggest that the hypothesis should be rejected in the all classes of collision\nsystems and centralities of PHENIX-RHIC measurements. However, the application\nof the least-squares test statistic with systematic errors included shows that\nfor the collision system Au-Au at $\\sqrt{s_{NN}} = 62.4$ GeV the hypothesis\ncould not be rejected in general.", "category": "nucl-th" }, { "text": "A quasiparticle equation of state with a phenomenological critical point: We propose a hybrid parameterization of a quasiparticle equation of state,\nwhere a critical point is implemented phenomenologically. In this approach, a\nquasiparticle model with finite chemical potential is used to describe the\nquark-gluon plasma phase by fitting to the lattice quantum chromodynamics data\nat high temperature. On the other hand, the hadronic resonance gas model with\nexcluded volume correction is employed for the hadronic phase. An interpolation\nscheme is implemented so that the phase transition is a smooth crossover when\nthe chemical potential is smaller than a critical value, or otherwise\napproximately of first order according to Ehrenfest's classification. Also, the\nthermodynamic consistency is guaranteed for the equation of state related to\nboth the quasiparticle model and the implementation of the critical point.", "category": "nucl-th" }, { "text": "Smallness of the imaginary part of the eta-nucleus scattering length: In two recent analyses of eta meson production a very small imaginary part\nwas obtained for the eta-He3 scattering length, which is in contradiction with\nmost theoretical predictions. In this report a plausible explanation is given\nto this unexpectedly weak absorption by suppression of the two main\ninelasticity channels. It is stressed that the real and imaginary parts of the\nelementary scattering length do not necessarily always have the same isospin\nalgebraic and spatial properties in a nuclear environment and caution should be\nexercised in their use in multiple scattering calculations and even\nconstructing simple optical potentials.", "category": "nucl-th" }, { "text": "Macroscopic approximation to relativistic kinetic theory from a\n nonlinear closure: We use a macroscopic description of a system of relativistic particles based\non adding a nonequilibrium tensor to the usual hydrodynamic variables. The\nnonequilibrium tensor is linked to relativistic kinetic theory through a\nnonlinear closure suggested by the Entropy Production Principle; the evolution\nequation is obtained by the method of moments, and together with\nenergy-momentum conservation closes the system. Transport coefficients are\nchosen to reproduce second order fluid dynamics if gradients are small. We\ncompare the resulting formalism to exact solutions of Boltzmann's equation in\n0+1 dimensions and show that it tracks kinetic theory better than second order\nfluid dynamics.", "category": "nucl-th" }, { "text": "Bose-Einstein condensation of pions in heavy-ion collisions at the CERN\n Large Hadron Collider (LHC) energies: We analyse in detail the possibility of Bose-Einstein condensation of pions\nproduced in heavy-ion collisions at the beam energy $\\sqrt{s_{\\rm NN}}$ = 2.76\nTeV. Our approach is based on the chemical non-equilibrium thermal model of\nhadron production which has been generalised to include separately the\ncontribution from the local zero-momentum state. In order to study both the\nhadronic multiplicities and the transverse-momentum spectra, we use the Cracow\nfreeze-out model which parameterises the flow and space-time geometry of the\nsystem at freeze-out in a very economic way. Our analysis indicates that about\n5% of all pions may form the Bose-Einstein condensate.", "category": "nucl-th" }, { "text": "Deformed Nuclei in a Chiral Model: We investigate the deformation properties of atomic nuclei in a hadronic\nchiral SU_f(3) model approach. The parameters are fitted to hadron mass\nproperties and adjustments for spherical finite nuclei have been performed.\nUsing these parameters the deformation of a series of light and heavy nuclei\nare obtained in a two-dimensional self-consistent calculation. In addition we\ndiscuss a case of superdeformation in a heavy nucleus.", "category": "nucl-th" }, { "text": "Production of eta mesons in nucleon-nucleon collisions: A microscopic calculation of near-threshold eta-meson production in the\nreaction NN -> NNeta is presented. It is assumed that the eta meson is produced\nvia direct emission and via elementary rescattering processes MN -> etaN of\nvarious mesons M = pi, rho, etc. As a novel feature the amplitudes for the\nlatter production mechanism are taken from a multi-channel meson-exchange model\nof the pi N system developed by the Juelich group which contains explicitly the\nchannels pi N, rho N, eta N, sigma N, and pi Delta. Furthermore, effects of the\nNN interaction in the final as well as in the initial state are taken into\naccount microscopically. Our results are compared with recent data from the\nCOSY and CELSIUS accelerator facilities. Reasonable agreement with available\nnear-threshold cross section data for the reactions pp -> ppeta, pn -> pneta,\nand pn -> deta is found.", "category": "nucl-th" }, { "text": "Threshold Two-Pion Photo- and Electroproduction: More neutrals than\n expected: We present an exploratory study of two pion photo-- and electroproduction off\nthe nucleon in the threshold region. To calculate the pertinent amplitudes, we\nmake use of heavy baryon chiral perturbation theory. We show that due to finite\nchiral loops the production cross section for final states with two neutral\npions is considerably enhanced. The experimental implications are briefly\ndiscussed.", "category": "nucl-th" }, { "text": "Open-Shell Nuclei from No-Core Shell Model with Perturbative Improvement: We introduce a hybrid many-body approach that combines the flexibility of the\nNo-Core Shell Model (NCSM) with the efficiency of Multi-Configurational\nPerturbation Theory (MCPT) to compute ground- and excited-state energies in\narbitrary open-shell nuclei in large model spaces. The NCSM in small model\nspaces is used to define a multi-determinantal reference state that contains\nthe most important multi-particle multi-hole correlations and a subsequent\nsecond-order MCPT correction is used to capture additional correlation effects\nfrom a large model space. We apply this new ab initio approach for the\ncalculation of ground-state and excitation energies of even and odd-mass\ncarbon, oxygen, and fluorine isotopes and compare to large-scale NCSM\ncalculations that are computationally much more expensive.", "category": "nucl-th" }, { "text": "Complex phase structure of the meson-baryon $T$-matrix: The full complex phase structure of the meson-baryon reaction amplitude in\ncoupled channels approach is investigated, including also the photon-baryon\nchannel. The result may be viewed as a generalization of the well-known\nWatson's theorem. Furthermore, the complex phase structure is exhibited for the\npole and nonpole parts of the reaction amplitude in such a way that it will\nserve as a convenient common starting point for constructing models with\ndifferent levels of approximation, in particular, for building isobar models\nwhere the basic properties of the $S$-matrix can be maintained. Such models\nshould be useful, especially, in coupled multichannel calculations, where a\nlarge amount of experimental data are considered in resonance analyses, a\nsituation encountered in modern baryon spectroscopy. In particular, it is shown\nthat the unitarity of the pole part of the $T$-matrix arises automatically from\nthe dressing mechanism inherent in the basic scattering equation. This implies\nthat no separate conditions are required for making this part of the resonance\namplitude unitary as it has been done in some of the existing isobar models.", "category": "nucl-th" }, { "text": "Collective model for cluster motion in $^8$Be, $^{12}$C, and $^{16}$O\n systems: A microscopic $n\\alpha$ cluster model was applied to $^{8}$Be, $^{12}$C, and\n$^{16}$O systems to investigate cluster motion in the ground state and radial\nexcitation. In the microscopic calculation of $^{12}$C and $^{16}$O using the\ngenerator coordinate method with the coordinate $D$ of the $\\alpha$-$\\alpha$\ndistance, excited states were obtained as the large-amplitude mode built on the\nground state. A collective model was constructed to describe the cluster motion\nof these states by utilizing inputs from the microscopic cluster model such as\nthe norm kernel and energy expectation values. Furthermore, the cluster model\nwas extended by introducing the imaginary part of the coordinate $D$ to\nincorporate the dynamical effects on the collective mass. The collective wave\nfunction obtained with the collective model was found to be in reasonable\nagreement with the results of the generator coordinate method for energies,\nroot-mean-square radii, and amplitude functions.", "category": "nucl-th" }, { "text": "Location of the QCD critical point predicted by holographic Bayesian\n analysis: We present results for a Bayesian analysis of the location of the QCD\ncritical point constrained by first-principles lattice QCD results at zero\nbaryon density. We employ a holographic Einstein-Maxwell-dilaton model of the\nQCD equation of state, capable of reproducing the latest lattice QCD results at\nzero and finite baryon chemical potential. Our analysis is carried out for two\ndifferent parametrizations of this model, resulting in confidence intervals for\nthe critical point location that overlap at one sigma. While samples of the\nprior distribution may not even predict a critical point, or produce critical\npoints spread around a large region of the phase diagram, posterior samples\nnearly always present a critical point at chemical potentials of $\\mu_{Bc} \\sim\n550 - 630$ MeV.", "category": "nucl-th" }, { "text": "Heavy Flavor Suppression: Boltzmann vs Langevin: The propagation of heavy flavor through the quark gluon plasma has been\ntreated commonly within the framework of Langevin dynamics, i.e. assuming the\nheavy flavor momentum transfer is much smaller than the light one. On the other\nhand a similar suppression factor $R_{AA}$ has been observed experimentally for\nlight and heavy flavors. We present a thorough study of the approximations\ninvolved by Langevin equation by mean of a direct comparison with the full\ncollisional integral within the framework of Boltzmann transport equation. We\nhave compared the results obtained in both approaches which can differ\nsubstantially for charm quark leading to quite different values extracted for\nthe heavy quark diffusion coefficient. In the case of bottom quark the\napproximation appears to be quite reasonable.", "category": "nucl-th" }, { "text": "Effect of cluster transfer on neutron-rich nuclide production around\n N=126 in multinucleon transfer reactions: The cluster transfer in multinucleon transfer reactions near Coulomb barrier\nenergies is implemented into the master equations in dinuclear system model, in\nwhich the deuteron, triton, $^{3}$He and $\\alpha$ are taken into account. The\neffects of cluster transfer and dynamical deformation on the formation of\nprimary and secondary fragments are systematically investigated. It is found\nthat the inclusion of cluster transfer is favorable the fragment formation with\nincreasing the transferring nucleons and leads to a broad mass distribution.\nThe isotopic cross sections of elements W, Os, Rn and Fr in the reaction of\n$^{136}$Xe+$^{208}$Pb at the incident energy of E$_{c.m.}$ = 450 MeV are nicely\nconsistent with the Argonne data. The new neutron-rich isotopes of wolfram and\nosmium are predicted with cross sections above 10 nb. The production mechanism\nof neutron-rich heavy nuclei around N = 126 in the reactions of $^{58,64,72}$Ni\n+ $^{198}$Pt is investigated thoroughly. The cross sections for producing the\nneutron-rich isotopes of platinum, iridium, osmium and rhenium in the\nmultinucleon transfer reactions of $^{64}$Ni + $^{198}$Pt and $^{72}$Ni +\n$^{198}$Pt at the center of mass energies of 220 MeV and 230 MeV are estimated\nand proposed for the future experiments.", "category": "nucl-th" }, { "text": "Matter effects on $\u03b7$ and $\u03b7'$ mesons: We show how the nuclear medium affects the masses of the $\\eta$ and $\\eta'$\nmesons. The change should be easily detectable for dense matter and/or strong\n$\\eta(\\eta')N\\bar N$ coupling. We also find that the $\\eta-\\eta'$ mixing angle\nis less in magnitude in the nuclear matter than in vacuum.", "category": "nucl-th" }, { "text": "Momentum dependent nucleon-nucleon contact interaction from a\n relativistic Lagrangian: A complete set of parity- and time-reversal conserving relativistic\nnucleon-nucleon contact operators is identified up to the order $O(p^4)$ of the\nexpansion in soft momenta $p$. A basis is also provided for the corresponding\nnon-relativistic operators contributing in the general reference frame. We show\nthat the non-relativistic expansions of the relativistic operators involve\ntwenty-six independent combinations, two starting at $O(p^0)$, seven at order\n$O(p^2)$ and seventeen at order $O(p^4)$. This gives supporting evidence to the\nexistence of two free low-energy constants which parametrize an interaction\ndepending on the total nucleon pair momentum ${\\bf P}$, and were recently found\nto be instrumental for the resolution of the long standing $A_y$ problem in\nlow-energy $p-d$ scattering. Furthermore, all remaining ${\\bf P}$-dependent\ninteractions at the same order are uniquely determined as relativistic\ncorrections.", "category": "nucl-th" }, { "text": "Momentum-space calculation of proton-deuteron scattering including\n Coulomb and irreducible three-nucleon forces: Three-nucleon scattering equations with irreducible three-nucleon force are\nsolved in momentum-space. The Coulomb interaction between the two protons is\nincluded using the method of screening and renormalization. The need for the\nrenormalization of the scattering amplitudes is demonstrated numerically. The\nCoulomb and Urbana IX three-nucleon force effects on the observables of elastic\nproton-deuteron scattering and breakup are studied.", "category": "nucl-th" }, { "text": "Photon electroproduction off nuclei in the $\u0394$-resonance region: The cross section for the $A(e,e'\\gamma)A$ reaction is calculated,\ninvestigating the contribution from the nuclear target with respect to the\nradiative corrections from the electron. The reaction mechanism is studied for\nphoton emission in the $\\Delta$-resonance region, varying the scattering\ngeometry and analyzing the most favourable kinematical conditions to extract\ninformation on the nuclear system.", "category": "nucl-th" }, { "text": "Tracing baryon and electric charge transport in isobar collisions: It is of fundamental interest to understand the carrier of conserved quantum\ncharges within protons and nuclei at high energy. Preliminary data from isobar\ncollisions at RHIC reveal a scaled net-baryon to net-electric charge ratio\n($B/\\Delta Q \\times \\Delta Z/A$) at mid-rapidity between 1.2 and 2, consistent\nwith string junction model predictions. Here, we compute the initial stage\nscaled net-baryon to net-electric charge ratio for isobar collisions. Our model\nincorporates a realization of the string junction model and models the nuclear\nstructure. Our predictions identify the baseline expectations for such\nmeasurement and quantify the impact of the nuclear structure.", "category": "nucl-th" }, { "text": "ADG: Automated generation and evaluation of many-body diagrams III.\n Bogoliubov in-medium similarity renormalization group formalism: The goal of the present paper is twofold. First, a novel expansion many-body\nmethod applicable to superfluid open-shell nuclei, the so-called Bogoliubov\nin-medium similarity renormalization group (BIMSRG) theory, is formulated. This\ngeneralization of standard single-reference IMSRG theory for closed-shell\nsystems parallels the recent extensions of coupled cluster, self-consistent\nGreen's function or many-body perturbation theory. Within the realm of IMSRG\ntheories, BIMSRG provides an interesting alternative to the already existing\nmulti-reference IMSRG (MR-IMSRG) method applicable to open-shell nuclei.\n The algebraic equations for low-order approximations, i.e., BIMSRG(1) and\nBIMSRG(2), can be derived manually without much difficulty. However, such a\nmethodology becomes already impractical and error prone for the derivation of\nthe BIMSRG(3) equations, which are eventually needed to reach high accuracy.\nBased on a diagrammatic formulation of BIMSRG theory, the second objective of\nthe present paper is thus to describe the third version (v3.0.0) of the ADG\ncode that automatically (1) generates all valid BIMSRG(n) diagrams and (2)\nevaluates their algebraic expressions in a matter of seconds. This is achieved\nin such a way that equations can easily be retrieved for both the flow equation\nand the Magnus expansion formulations of BIMSRG.\n Expanding on this work, the first future objective is to numerically\nimplement BIMSRG(2) (eventually BIMSRG(3)) equations and perform ab initio\ncalculations of mid-mass open-shell nuclei.", "category": "nucl-th" }, { "text": "Asymptotics of neutron Cooper pair in weakly bound nuclei: Asymptotic form of neutron Cooper pair penetrating to the exterior of nuclear\nsurface is investigated with the Bogoliubov theory for the superfluid Fermions.\nBased on a two-particle Schr\\\"{o}dinger equation governing the Cooper pair wave\nfunction and systematic studies for both weakly bound and stable nuclei, the\nCooper pair is shown to be spatially correlated even in the asymptotic large\ndistance limit, and the penetration length of the pair condensate is revealed\nto be universally governed by the two-neutron separation energy $S_{2n}$ and\nthe di-neutron mass $2m$.", "category": "nucl-th" }, { "text": "Exact versus Taylor-expanded energy density in the study of the neutron\n star crust-core transition: The importance of the fourth and higher order terms in the Taylor series\nexpansion of the energy of the isospin asymmetric nuclear matter in the study\nof the neutron star crust-core phase transition is investigated using the\nfinite range simple effective interaction. Analytic expressions for the\nevaluation of the second and fourth order derivative terms in the Taylor series\nexpansion for any general finite range interaction of Yukawa, exponential or\nGaussian form have been obtained. The effect of the nuclear matter\nincompressibility, symmetry energy and slope parameters on the predictions for\nthe crust-core transition density is examined. The crustal moment of inertia is\ncalculated and the prediction for the radius of the Vela pulsar is analyzed\nusing different equations of state.", "category": "nucl-th" }, { "text": "P and T odd effects in deuteron in the Reid potential: The $P$ and $T$ odd deuteron multipoles are calculated in the Reid\nnucleon-nucleon potential in the chiral limit $m_{\\pi}\\to 0$. The contact\ncurrent generated by the $\\pi$-meson exchange does not contribute to the\nanapole moment. The contact current generated by the vector meson exchange is\nnegligible in comparison with other contributions of vector mesons. The result\nfor the deuteron electric dipole moment is of great interest because of the\nexperiment on its measurement discussed in Brookhaven. The deuteron\nphotodisintegration cross section asymmetry at the threshold is also\ncalculated. It is shown that its value strongly depends on the tensor forces\nand d-wave contribution to the deuteron wave function.", "category": "nucl-th" }, { "text": "J/psi production at mid and forward rapidity at RHIC: We calculate the rapidity dependence of $J/\\psi$ nuclear modification factor\nand averaged transverse momentum square in heavy ion collisions at RHIC in a\n3-dimensional transport approach with regeneration mechanism.", "category": "nucl-th" }, { "text": "Analysis of the pp-->pp, pid-->pid, and pid-->pp Scattering Data: A combined analysis of the main reactions of the two-baryon system (pp-->pp,\npid-->pid, and pid-->pp) over the sqrt{s} interval from pion threshold to 2.4\nGeV has been completed. The overall phase in pid-->pp has now been determined.\nThe combined analysis has resulted in an improved fit to the pid elastic and\npid-->pp databases.", "category": "nucl-th" }, { "text": "Small-$x$ Asymptotics of the Gluon Helicity Distribution: We determine the small-$x$ asymptotics of the gluon helicity distribution in\na proton at leading order in perturbative QCD at large $N_c$. To achieve this,\nwe begin by evaluating the dipole gluon helicity TMD at small $x$. In the\nprocess we obtain an interesting new result: in contrast to the unpolarized\ndipole gluon TMD case, the operator governing the small-$x$ behavior of the\ndipole gluon helicity TMD is different from the operator corresponding to the\npolarized dipole scattering amplitude (used in our previous work to determine\nthe small-$x$ asymptotics of the quark helicity distribution). We then\nconstruct and solve novel small-$x$ large-$N_c$ evolution equations for the\noperator related to the dipole gluon helicity TMD. Our main result is the\nsmall-$x$ asymptotics for the gluon helicity distribution: $\\Delta G \\sim\n\\left( \\tfrac{1}{x} \\right)^{\\alpha_h^G}$ with $\\alpha_h^G = \\tfrac{13}{4\n\\sqrt{3}} \\, \\sqrt{\\tfrac{\\alpha_s \\, N_c}{2 \\pi}} \\approx 1.88 \\,\n\\sqrt{\\tfrac{\\alpha_s \\, N_c}{2 \\pi}}$. We note that the power $\\alpha_h^G$ is\napproximately 20$\\%$ lower than the corresponding power $\\alpha_h^q$ for the\nsmall-$x$ asymptotics of the quark helicity distribution defined by $\\Delta q\n\\sim \\left( \\tfrac{1}{x} \\right)^{\\alpha_h^q}$ with $\\alpha_h^q =\n\\tfrac{4}{\\sqrt{3}} \\, \\sqrt{\\tfrac{\\alpha_s \\, N_c}{2 \\pi}} \\approx 2.31 \\,\n\\sqrt{\\tfrac{\\alpha_s \\, N_c}{2 \\pi}}$ found in our earlier work.", "category": "nucl-th" }, { "text": "Electric Properties of One-Neutron Halo Nuclei in Halo EFT: We exploit the separation of scales in weakly-bound nuclei to compute E2\ntransitions and electric form factors in a Halo EFT framework. The relevant\ndegrees of freedom are the core and the halo neutron. The EFT expansion is\ncarried out in powers of $R_{core}/R_{halo}$, where $R_{core}$ and $R_{halo}$\ndenote the length scales of the core and halo, respectively. We include the\nstrong $s$-wave and $d$-wave interactions by introducing dimer fields. The\ndimer propagators are regulated by employing the power divergence subtraction\nscheme and matched to the effective range expansion in the respective\nchannel.Electromagnetic interactions are included via minimal substitution in\nthe Lagrangian. We demonstrate that, depending on the observable and respective\npartial wave, additional local gauge-invariant operators contribute in LO, NLO\nand higher orders.", "category": "nucl-th" }, { "text": "Spin observables in antiproton-proton to AntiLambda-Lambda and\n density-matrix constraints: The positivity conditions of the spin density matrix constrain the spin\nobservables of the reaction antiproton-proton to AntiLambda-Lambda, leading to\nmodel-independent, non-trivial inequalities. The formalism is briefly presented\nand examples of inequalities are provided.", "category": "nucl-th" }, { "text": "Ion induced quark-gluon implosion: We investigate nuclear fragmentation in the central proton-nucleus and\nnucleus - nucleus collisions at the energies of LHC. We argue that within the\nsemi-classical approximation because of fast increase with energy of cross\nsections of soft and hard interactions each nucleon is stripped in the average\nprocess off ``soft'' partons and fragments into a collection of leading quarks\nand gluons with large $p_t$. Valence quarks and gluons are streaming in the\nopposite directions when viewed in the c.m. of the produced system. The\nresulting pattern of the fragmentation of the colliding nuclei leads to an\nimplosion of the quark and gluon constituents of the nuclei. The matter density\nproduced at the initial stage in the nucleus fragmentation region is estimated\nto be $\\geq$ 50 GeV/fm$^3$ at the LHC energies and probably $\\geq$ 10\nGeV/fm$^3$ at RHIC.", "category": "nucl-th" }, { "text": "Internal One-Particle Density Matrix for Bose-Einstein Condensates with\n Finite Number of Particles in a Harmonic Potential: Investigations on the internal one-particle density matrix in the case of\nBose-Einstein condensates with a finite number ($N$) of particles in a harmonic\npotential are performed. We solve the eigenvalue problem of the\nPethick-Pitaevskii-type internal density matrix and find a fragmented\ncondensate. On the contrary the condensate Jacobi-type internal density matrix\ngives complete condensation into a single state. The internal one-particle\ndensity matrix is, therefore, shown to be different in general for different\nchoices of the internal coordinate system. We propose two physically motivated\ncriteria for the choice of the adequate coordinate systems which give us a\nunique answer for the internal one-particle density matrix. One criterion is\nthat in the infinite particle number limit ($N=\\infty$) the internal\none-particle density matrix should have the same eigenvalues and eigenfunctions\nas those of the corresponding ideal Bose-Einstein condensate in the laboratory\nframe. The other criterion is that the coordinate of the internal one-particle\ndensity matrix should be orthogonal to the remaining $(N - 2)$ internal\ncoordinates. This second criterion is shown to imply the first criterion. It is\nshown that the internal Jacobi coordinate system satisfies these two criteria\nwhile the internal coordinate system adopted by Pethick and Pitaevskii for the\nconstruction of the internal one-particle density matrix does not. It is\ndemonstrated that these two criteria uniquely determine the internal\none-particle density matrix which is identical to that calculated with the\nJacobi coordinates. The relevance of this work concerning $\\alpha$-particle\ncondensates in nuclei, as well as bosonic atoms in traps, is pointed out.", "category": "nucl-th" }, { "text": "Delayed Collapse of Protoneutron Stars with Kaon Condensate: Equation of state with kaon condensate is derived for isentropic and\nneutrino-trapped matter. Both are important ingredients to study the delayed\ncollapse of protoneutron stars. Solving the TOV equation, we discuss the static\nproperties of protoneutron stars and implications for their delayed collapse.", "category": "nucl-th" }, { "text": "Relativistic fluctuating hydrodynamics with memory functions and colored\n noises: Relativistic dissipative hydrodynamics including hydrodynamic fluctuations is\nformulated by putting an emphasis on non-linearity and causality. As a\nconsequence of causality, dissipative currents become dynamical variables and\nnoises appeared in an integral form of constitutive equations should be colored\nones from fluctuation-dissipation relations. Nevertheless noises turn out to be\nwhite ones in its differential form when noises are assumed to be Gaussian. The\nobtained ifferential equations are very useful in numerical implementation of\nrelativistic fluctuating hydrodynamics.", "category": "nucl-th" }, { "text": "Superdeformation and clustering in $^{40}$Ca studied with\n Antisymmetrized Molecular Dynamics: Deformed states in $^{40}$Ca are investigated with a method of\nantisymmetrized molecular dynamics. Above the spherical ground state,\nrotational bands arise from a normal deformation and a superdeformation as well\nas an oblate deformation. The calculated energy spectra and $E2$ transition\nstrengths in the superdeformed band reasonably agree to the experimental data\nof the superdeformed band starting from the $0^+_3$ state at 5.213 MeV. By the\nanalysis of single-particle orbits, it is found that the superdeformed state\nhas particle-hole nature of an $8p$-$8h$ configuration. One of new findings is\nparity asymmetric structure with $^{12}$C+$^{28}$Si-like clustering in the\nsuperdeformed band. We predict that $^{12}$C+$^{28}$Si molecular bands may be\nbuilt above the superdeformed band due to the excitation of inter-cluster\nmotion. They are considered to be higher nodal states of the superdeformed\nstate. We also suggest negative-parity bands caused by the parity asymmetric\ndeformation.", "category": "nucl-th" }, { "text": "Self-consistent description of the halo nature of 31Ne with continuum\n and pairing correlations: Using a Glauber model with our relativistic fully microscopic structure model\ninput, we give a full description of the halo nature of 31Ne that includes a\nself-consistent use of pairing and continuum contributions that makes\npredictions consistent with reaction cross section measurements. Our\npredictions of total reaction and one-neutron removal cross sections of 31Ne on\na Carbon target were significantly enhanced compared with those of neighboring\nNeon isotopes, agreeing well with measurements at 240 MeV/nucleon and\nconsistent with a single neutron halo. Furthermore, our calculations of the\ninclusive longitudinal momentum distribution of the 30Ne and valence neutron\nresidues from the 31Ne breakup reaction indicate a dilute density distribution\nin coordinate space, another halo signature.", "category": "nucl-th" }, { "text": "Photoproduction of meson and baryon resonances in a chiral unitary\n approach: By means of a coupled channel non-perturbative unitary approach, it is\npossible to extend the strong constrains of Chiral Perturbation Theory to\nhigher energies. In particular, it is possible to reproduce the lowest lying\nresonances in meson-meson scattering up to 1.2 GeV using the parameters of the\nO(p^2) and O(p^4) Chiral Lagrangian. The meson baryon sector can also be\ntackled along similar lines. We report on an update of these results showing\nsome examples of photon induced reactions where the techniques have been\nrecently applied.", "category": "nucl-th" }, { "text": "Freeze Out Process with In-Medium Nucleon Mass: We investigate the kinetic freeze out scenario of a nucleon gas through a\nfinite layer. The in-medium mass modification of nucleons and it's impact on\nthe freeze out process is studied. A considerable modification of the\nthermodynamical parameters temperature, flow-velocity, energy density and\nparticle density has been found in comparison with evaluations which use a\nconstant vacuum nucleon mass.", "category": "nucl-th" }, { "text": "Nuclear interactions and net-proton number fluctuations in heavy ion\n collisions at the SIS18 accelerator: The effect of nuclear interactions on measurable net-proton number\nfluctuations in heavy ion collisions at the SIS18/GSI accelerator is\ninvestigated. The state of the art UrQMD model including interaction potentials\nis employed. It is found that the nuclear forces enhance the baryon number\ncumulants, as predicted from grand canonical thermodynamical models. The effect\nhowever is smeared out for proton number fluctuations due to iso-spin\nrandomization and global baryon number conservation, which decreases the\ncumulant ratios. For a rapidity acceptance window larger than $\\Delta y> 0.4$\nthe effects of global baryon number conservation dominate and all cumulant\nratios are significantly smaller than 1.", "category": "nucl-th" }, { "text": "Transport approaches for the Description of Intermediate-Energy\n Heavy-Ion Collisions: The transport approach is a useful tool to study dynamics of non-equilibrium\nsystems. For heavy-ion collisions at intermediate energies, where both the\nsmooth nucleon potential and the hard-core nucleon-nucleon collision are\nimportant, the dynamics are properly described by two families of transport\nmodels, i.e., the Boltzmann-Uehling-Uhlenbeck approach and the quantum\nmolecular dynamics approach. These transport models have been extensively used\nto extract valuable information of the nuclear equation of state, the nuclear\nsymmetry energy, and microscopic nuclear interactions from intermediate-energy\nheavy-ion collision experiments. On the other hand, there do exist deviations\non the predications and conclusions from different transport models. Efforts on\nthe transport code evaluation project are devoted in order to understand the\nmodel dependence of transport simulations and well control the main\ningredients, such as the initialization, the mean-field potential, the\nnucleon-nucleon collision, etc. A new era of accurately extracting nuclear\ninteractions from transport model studies is foreseen.", "category": "nucl-th" }, { "text": "Statistical multifragmentation model with discretized energy and the\n generalized Fermi breakup. I. Formulation of the model: The Generalized Fermi Breakup recently demonstrated to be formally equivalent\nto the Statistical Multifragmentation Model, if the contribution of excited\nstates are included in the state densities of the former, is implemented. Since\nthis treatment requires the application of the Statistical Multifragmentation\nModel repeatedly on the hot fragments until they have decayed to their ground\nstates, it becomes extremely computational demanding, making its application to\nthe systems of interest extremely difficult. Based on exact recursion formulae\npreviously developed by Chase and Mekjian to calculate the statistical weights\nvery efficiently, we present an implementation which is efficient enough to\nallow it to be applied to large systems at high excitation energies. Comparison\nwith the GEMINI++ sequential decay code shows that the predictions obtained\nwith our treatment are fairly similar to those obtained with this more\ntraditional model.", "category": "nucl-th" }, { "text": "Evolution of $N=20,28,50$ shell closures in the $ 20 \\leqslant Z\n \\leqslant 30$ region in deformed relativistic Hartree-Bogoliubov theory in\n continuum: Magicity, or shell closure, plays an important role in our understanding of\ncomplex nuclear phenomena. In this work, we employ one of the state-of-the-art\ndensity functional theories, the deformed relativistic Hartree-Bogoliubov\ntheory in continuum (DRHBc) with the density functional PC-PK1, to investigate\nthe evolution of the $N=20,28,50$ shell closures in the $ 20 \\leqslant Z\n\\leqslant 30$ region. We show how these three conventional shell closures\nevolve from the proton drip line to the neutron drip line by studying the\ncharge radii, two-neutron separation energies, two-neutron gaps, quadrupole\ndeformations, and single-particle levels. In particular, we find that in the $\n21 \\leqslant Z \\leqslant 27$ region, the $N=50$ shell closure disappears or\nbecomes quenched, mainly due to the deformation effects. Similarly, both\nexperimental data and theoretical predictions indicate that the $N=28$ shell\nclosure disappears in the Mn isotopic chain, also predominantly due to the\ndeformation effects. The DRHBc theory predicts the existence of the $N=20$\nshell closure in the Ca, Sc, and Ti isotopic chains, but the existing data for\nthe Ti isotopes suggests the contrary, and therefore more investigations are\nneeded.", "category": "nucl-th" }, { "text": "Suprathermal viscosity of dense matter: Motivated by the existence of unstable modes of compact stars that eventually\ngrow large, we study the bulk viscosity of dense matter, taking into account\nnon-linear effects arising in the large amplitude regime, where the deviation\nmu_Delta of the chemical potentials from chemical equilibrium fulfills mu_Delta\n> T. We find that this supra-thermal bulk viscosity can provide a potential\nmechanism for saturating unstable modes in compact stars since the viscosity is\nstrongly enhanced. Our study confirms previous results on strange quark matter\nand shows that the suprathermal enhancement is even stronger in the case of\nhadronic matter. We also comment on the competition of different weak channels\nand the presence of suprathermal effects in various color superconducting\nphases of dense quark matter.", "category": "nucl-th" }, { "text": "Strangeness $S=-1$ hyperon-nucleon interactions: chiral effective field\n theory vs. lattice QCD: Hyperon-nucleon interactions serve as basic inputs to studies of hypernuclear\nphysics and dense (neutron) stars. Unfortunately, a precise understanding of\nthese important quantities have lagged far behind that of the nucleon-nucleon\ninteraction due to lack of high precision experimental data. Historically,\nhyperon-nucleon interactions are either formulated in quark models or meson\nexchange models. In recent years, lattice QCD simulations and chiral effective\nfield theory approaches start to offer new insights from first principles. In\nthe present work, we contrast the state of art lattice QCD simulations with the\nlatest chiral hyperon-nucleon forces and show that the leading order\nrelativistic chiral results can already describe the lattice QCD data\nreasonably well. Given the fact that the lattice QCD simulations are performed\nwith pion masses ranging from the (almost) physical point to 700 MeV, such\nstudies provide a highly non-trivial check on both the chiral effective field\ntheory approaches as well as lattice QCD simulations. Nevertheless more precise\nlattice QCD simulations are eagerly needed to refine our understanding of\nhyperon-nucleon interactions.", "category": "nucl-th" }, { "text": "Relativistic viscous hydrodynamics for heavy-ion collisions: A\n comparison between the Chapman-Enskog and Grad methods: Derivations of relativistic second-order dissipative hydrodynamic equations\nhave relied almost exclusively on the use of Grad's 14-moment approximation to\nwrite $f(x,p)$, the nonequilibrium distribution function in the phase space.\nHere we consider an alternative Chapman-Enskog-like method, which, unlike\nGrad's, involves a small expansion parameter. We derive an expression for\n$f(x,p)$ to second order in this parameter. We show analytically that while\nGrad's method leads to the violation of the experimentally observed\n$1/\\sqrt{m_T}$ scaling of the longitudinal femtoscopic radii, the alternative\nmethod does not exhibit such an unphysical behavior. We compare numerical\nresults for hadron transverse-momentum spectra and femtoscopic radii obtained\nin these two methods, within the one-dimensional scaling expansion scenario.\nMoreover, we demonstrate a rapid convergence of the Chapman-Enskog-like\nexpansion up to second order. This leads to an expression for $\\delta f(x,p)$\nwhich provides a better alternative to Grad's approximation for hydrodynamic\nmodeling of relativistic heavy-ion collisions.", "category": "nucl-th" }, { "text": "Faddeev Calculation of the Hypertriton using the SU_6 Quark-Model\n Nucleon-Nucleon and Hyperon-Nucleon Interactions: Quark-model nucleon-nucleon and hyperon-nucleon interactions by the Kyoto-\nNiigata group are applied to the hypertriton calculation in a new three-cluster\nFaddeev formalism using the two-cluster resonating-group method kernels. The\nmost recent model, fss2, gives a reasonable result similar to the Nijmegen\nsoft-core model NSC89, except for an appreciable contributions of higher\npartial waves.", "category": "nucl-th" }, { "text": "Baryon and meson screening masses: In a strongly-coupled quark-gluon plasma, collective excitations of gluons\nand quarks should dominate over the excitation of individual quasi-free gluon\nand quark modes. To explore this possibility, we computed screening masses for\nground-state light-quark mesons and baryons at leading-order in a\nsymmetry-preserving truncation scheme for the Dyson-Schwinger equations using a\nconfining formulation of a contact-interaction at nonzero temperature. Meson\nscreening masses are obtained from Bethe-Salpeter equations; and baryon\nanalogues from a novel construction of the Faddeev equation, which employs an\nimproved quark-exchange approximation in the kernel. Our treatment implements a\ndeconfinement transition that is coincident with chiral symmetry restoration in\nthe chiral limit, when both transitions are second order. Despite\ndeconfinement, in all T=0 bound-state channels, strong correlations persist\nabove the critical temperature, T>T_c; and, in the spectrum defined by the\nassociated screening masses, degeneracy between parity-partner correlations is\napparent for T >1.3T_c. Notwithstanding these results, there are reasons\n(including Golberger-Treiman relations) to suppose that the inertial masses of\nlight-quark bound-states, when they may be defined, vanish at the deconfinement\ntemperature; and that this is a signal of bound-state dissolution. Where a\nsensible comparison is possible, our predictions are consistent with results\nfrom contemporary numerical simulations of lattice-regularised QCD.", "category": "nucl-th" }, { "text": "Symmetry-unrestricted Skyrme mean-field study of heavy nuclei: In the light of recent experimental developments, increasing attention is\ndevoted to nuclear phenomena related to rotational excitations of exotic\nintrinsic nuclear configurations that often lack symmetries present in the\nmajority of nuclei. Examples include configurations with a non-vanishing\noctupole moment. In order to describe this kind of states, we have developed a\nnew computer code to solve the self-consistent mean-field equations, able to\nuse most of today's effective Skyrme interactions and working in\ncoordinate-space. We report on the development of MOCCa, a code based on the\nsame principles as EV8, but offering the user individual control on many\nsymmetry assumptions. In addition, the HF+BCS pairing treatment of EV8 has been\ngeneralised to the full machinery of Hartree-Fock-Bogoliubov transformations.\nWe discuss as example the static fission barrier of $^{226}$Ra, prefacing\nextended studies in the region, using the recent series of Skyrme\nparameterizations SLy5s1 through SLy5s8.", "category": "nucl-th" }, { "text": "Properties of superheavy nuclei with Z = 124: We employ Relativistic Mean Field (RMF) model with NL3 parametrization to\ninvestigate the ground state properties of superheavy nucleus, Z = 124. The\nnuclei selected (from among complete isotopic series) for detailed\ninvestigation show that the nucleon density at the center is very low and\ntherefore, these nuclei can be treated as semi-bubble nuclei. The considerable\nshell gap appears at neutron numbers N = 172, 184 and 198 showing the magicity\ncorresponding to these numbers. The results are compared with the\nmacro-microscopic Finite Range Droplet Model (FRDM) wherever possible.", "category": "nucl-th" }, { "text": "Chiral O(Q^4) two-body operators for s-wave pion photoproduction on the\n NN system: The two-body currents for s-wave pion photoproduction on the NN system are\nderived to O(Q^4) in chiral perturbation theory. For the interesting case of\n3S1 <-> 1S0 transitions, we show that an axial isovector two-nucleon contact\nterm connects the short-distance physics of pion photoproduction to pion\nproduction and several important electroweak reactions. We also find that the\nstandard chiral Lagrangian gives a gamma pi pi N N vertex that have not been\nexplicitly mentioned in previous literature. The corresponding Feynman rule is\npresented here and some processes where it should be important are briefly\ndiscussed.", "category": "nucl-th" }, { "text": "Backbending phenomena in light nuclei at A~60 mass region: Recent studies of the backbending phenomenon in medium light weight nuclei\nnear A~60 expanded greatly our interest about how the single particle orbits\nare nonlinearly affected by the collective motion. As a consequence we have\napplied a modi…ed version of the exponential model with the inclusion of\nparing correlation to describe the energy spectra of the ground state bands\nand/or the backbending phenomenon in mass region at A~60. A firm conclusion is\nobtained concerning the successful validity of the proposed modified model in\ndescribing the backbending phenomenon in this region. Comparison with different\ntheoretical descriptions is discussed.", "category": "nucl-th" }, { "text": "Quenching of Gamow-Teller strengths and two particle -- two hole\n configurations: We apply the charge-exchange subtracted second random-phase approximation\n(SSRPA), based on Skyrme functionals, to investigate Gamow-Teller resonances in\nseveral closed-shell and closed-subshell nuclei, located in different regions\nof the nuclear chart. After having discussed the SSRPA findings obtained within\ndifferent approximation schemes in $^{48}$Ca, we compare our results with\n{\\it{ab-initio}} coupled-cluster predictions available for C and O isotopes,\nwhere two-body currents are included. Our integrated strenghts, obtained by\nusing one-body transition operators, are lower compared to the corresponding\n{\\it{ab-initio}} results. This indicates that, within our model, quenching\neffects are mainly driven by the inclusion of two particle - two hole\nconfigurations and that the role of a two-body contribution in the transition\noperator is less important than in the coupled-cluster approach. By analyzing\nheavier nuclei, $^{90}$ Zr and $^{132}$Sn, we confirm the same conclusions that\nwe have recently drawn for $^{48}$Ca: the inclusion of two particle - two hole\nconfigurations is very effective in our model for providing strengths which are\nsignificantly more quenched than in other theoretical models and, thus, in\nbetter agreement with the experimental measurements. This occurs because two\nparticle - two hole configurations have a density which strongly increases with\nthe excitation energy. Their inclusion thus pushes a significant amount of the\nstrength to higher energies, compared to what happens in other theoretical\nmodels, reducing in this way the cumulative sum of the strength up to\nexcitation energies around 20-30 MeV.", "category": "nucl-th" }, { "text": "Enhanced effect of quark mass variation in 229Th and limits from Oklo\n data: The effects of the variation of the dimensionless strong interaction\nparameter Xq=mq/Lambda{QCD} (mq is the quark mass, Lambda{QCD} is the QCD\nscale) are enhanced about 1.5 x 10**5 times in the 7.6 eV \"nuclear clock\"\ntransition between the ground and first excited states in the 229Th nucleus and\nabout 1 x 10**8 times in the relative shift of the 0.1 eV compound resonance in\n150Sm.The best terrestrial limit on the temporal variation of the fundamental\nconstants, |delta(Xq)/Xq| < 4 x 10**-9 at 1.8 billion years ago (|d(Xq/Xq)/dt|\n< 2.2 x 10**-18 y**-1), is obtained from the shift of this Sm resonance derived\nfrom the Oklo natural nuclear reactor data. The results for 229Th and 150Sm are\nobtained by extrapolation from light nuclei where the many-body calculations\ncan be performed more accurately. The errors produced by such extrapolation may\nbe smaller than the errors of direct calculations in heavy nuclei. The\nextrapolation results are compared with the \"direct\" estimates obtained using\nthe Walecka model. A number of numerical relations needed for the calculations\nof the variation effects in nuclear physics and atomic spectroscopy have been\nobtained: for the nuclear binding energy delta(E)/E ~ -1.45 delta(mq)/mq, for\nthe spin-orbit intervals delta(Eso)/Eso ~ -0.22 delta(mq)/mq, for the nuclear\nradius delta(r)/r ~ 0.3 delta(mq)/mq (in units of Lambda{QCD}); for the shifts\nof nuclear resonances and weakly bound energy levels delta(Er) ~ 10\ndelta(Xq)/Xq MeV.", "category": "nucl-th" }, { "text": "The structure of the QED-Vacuum and Electron-Positron Pair Production in\n Super-Intense, pulsed Laser Fields: We discuss electron-positron pair-production by super-intense, short laser\npulses off the physical vacuum state locally deformed by (stripped) nuclei with\nlarge nuclear charges. Consequences of non-perturbative vacuum polarisation\nresulting from such a deformation are shortly broached. Production\nprobabilities per pulse are calculated.", "category": "nucl-th" }, { "text": "Scale Dependence of Nucleon-Nucleon Potentials: The scale-dependence of the nucleon-nucleon interaction, which in recent\nyears has been extensively analysed within the context of chiral effective\nfield theory, is, in fact, inherent in any potential models constrained by a\nfit to scattering data. A comparison between a purely phenomenological\npotential and local interactions derived from chiral effective field theory\nsuggests that--thanks to the ability to describe nucleon-nucleon scattering at\nhigher energies, as well as the deuteron momentum distribution extracted from\nelectro-disintegration data--phenomenological potentials are best suited for\nthe description of nuclear dynamics at the scale relevant to neutron star\nmatter.", "category": "nucl-th" }, { "text": "The optical model potential of the $\u03a3$ hyperon in nuclear matter: We present our attempts to determine the optical model potential $U_\\Sigma =\nV_\\Sigma -iW_\\Sigma$ of the $\\Sigma$ hyperon in nuclear matter. We analyze the\nfollowing sources of information on $U_\\Sigma$: $\\Sigma N$ scattering,\n$\\Sigma^-$ atoms, and final state interaction of $\\Sigma$ hyperons in the\n$(\\pi,K^+)$ and $(K^-.\\pi)$ reactions on nuclear targets. We conclude that\n$V_\\Sigma$ is repulsive inside the nucleus and has a shallow a tractive pocket\nat the nuclear surface. These features of $V_\\Sigma$ are consistent with the\nNijmegen model F of the hyperon-nucleon interaction.", "category": "nucl-th" }, { "text": "Meson-exchange currents and quasielastic predictions for\n neutrino-nucleus scattering: We review some recent progress in the study of electroweak interactions in\nnuclei within the SuSAv2-MEC model. The model has the capability to predict\n(anti)neutrino scattering observables on different nuclei. The theoretical\npredictions are compared with the recent T2K $\\nu_\\mu-^{16}$O data and good\nagreement is found at all kinematics. The results are very similar to those\nobtained for $\\nu_\\mu-^{12}$C scattering, except at low energies, where some\ndifferences emerge. The role of meson-exchange currents in the two-particle\ntwo-hole channel is analyzed in some detail. In particular it is shown that the\ndensity dependence of these contributions is different from what is found for\nthe quasielastic response.", "category": "nucl-th" }, { "text": "Thermal twin stars within a hybrid equation of state based on a nonlocal\n chiral quark model compatible with modern astrophysical observations: We investigate the extension to finite temperatures and neutrino chemical\npotentials of a recently developed nonlocal chiral quark model approach to the\nequation of state of neutron star matter. We consider two light quark flavors\nand current-current interactions in the scalar-pseudoscalar, vector, and\ndiquark pairing channels, where the nonlocality of the currents is taken into\naccount by a Gaussian form factor that depends on the spatial components of the\n4-momentum. Within this framework, we analyze order parameters, critical\ntemperatures, phase diagrams, equations of state, and mass-radius relations for\ndifferent temperatures and neutrino chemical potentials. For parameters of the\nmodel that are constrained by recent multi-messenger observations of neutron\nstars, we find that the mass-radius diagram for isothermal hybrid star\nsequences exhibits the thermal twin phenomenon for temperatures above 30 MeV.", "category": "nucl-th" }, { "text": "Linearly stable and causal relativistic first-order spin hydrodynamics: We derive equations of motion for dissipative spin hydrodynamics from kinetic\ntheory up to first order in a gradient expansion. Choosing a specific form of\nthe matching conditions, relating the change in the spin potential to the spin\ndiffusion and spin energy, we then show that the equations of motion,\nlinearized around homogeneous global equilibrium, are causal and stable in any\nLorentz frame, if certain sufficient conditions on the transport coefficients\nare fulfilled.", "category": "nucl-th" }, { "text": "Effective pseudopotential for energy density functionals with higher\n order derivatives: We derive a zero-range pseudopotential that includes all possible terms up to\nsixth order in derivatives. Within the Hartree-Fock approximation, it gives the\naverage energy that corresponds to a quasi-local nuclear Energy Density\nFunctional (EDF) built of derivatives of the one-body density matrix up to\nsixth order. The direct reference of the EDF to the pseudopotential acts as a\nconstraint that divides the number of independent coupling constants of the EDF\nby two. This allows, e.g., for expressing the isovector part of the functional\nin terms of the isoscalar part, or vice versa. We also derive the analogous set\nof constraints for the coupling constants of the EDF that is restricted by\nspherical, space-inversion, and time-reversal symmetries.", "category": "nucl-th" }, { "text": "Nonmesonic Weak Decay of $\u039b$ Hypernuclei: The Three--Nucleon\n Induced Mode: The nonmesonic weak decay of $\\Lambda$ hypernuclei is studied within a\nmicroscopic diagrammatic approach which is extended to include the\nthree--nucleon induced mechanism. We adopt a nuclear matter formalism which,\nthrough the local density approximation, allows us to model finite hypernuclei,\na one--meson--exchange weak transition potential and a Bonn nucleon--nucleon\nstrong potential. One--, two-- and three--nucleon induced weak decay rates are\npredicted for $^{12}_\\Lambda$C by including ground state correlations up to\nsecond order in the nucleon--nucleon potential and the recoil of the residual\nnucleus. Three--nucleon stimulated decays, $\\Lambda NNN\\to nNNN$ ($N=n$ or\n$p$), are considered here for the first time. The obtained decay rates compare\nwell with the latest KEK and FINUDA data. The three--nucleon induced rate turns\nout to be dominated by $nnp$-- and $npp$--induced decays, it amounts to $\\sim$\n7\\% of the total nonmesonic rate and it is $\\sim 1/2$ of the neutron--induced\ndecay rate. The reduction effect of the nuclear recoil is particularly relevant\nfor the three--nucleon induced rates ($\\sim$ 15\\%), less important for the\ntwo--nucleon induced rates ($\\sim$ 4\\%) and negligible for the one--nucleon\ninduced rates. Given the non--negligible size of the three--nucleon induced\ncontribution and consequently its importance in the precise determination of\nthe complete set of decay rates, new measurements and/or experimental analysis\nare encouraged.", "category": "nucl-th" }, { "text": "The isospin quartic term in the kinetic energy of neutron-rich nucleonic\n matter: The energy of a free gas of neutrons and protons is well known to be\napproximately isospin parabolic with a negligibly small quartic term of only\n$0.45$ MeV at the saturation density of nuclear matter $\\rho_0=0.16/\\rm{fm}^3$.\nUsing an isospin-dependent single-nucleon momentum distribution including a\nhigh (low) momentum tail (depletion) with its shape parameters constrained by\nrecent high-energy electron scattering and medium-energy nuclear\nphotodisintegration experiments as well as the state-of-the-art calculations of\nthe deuteron wave function and the equation of state of pure neutron matter\nnear the unitary limit within several modern microscopic many-body theories, we\nshow for the first time that the kinetic energy of interacting nucleons in\nneutron-rich nucleonic matter has a significant quartic term of\n$7.18\\pm2.52\\,\\rm{MeV}$. Such a large quartic term has significant\nramifications in determining the equation of state of neutron-rich nucleonic\nmatter using both terrestrial and astrophysical observables.", "category": "nucl-th" }, { "text": "Ab-initio no-core shell model study of $^{18-24}$Ne isotopes: We report \\textit{ab initio} no-core shell model (NCSM) study of $^{18-24}$Ne\nisotopes for energy spectra, electromagnetic properties, and point-proton radii\nusing three realistic $NN$ interactions. We have used inside nonlocal outside\nYukawa (INOY), charge-dependent Bonn 2000 (CDB2K) and the chiral\nnext-to-next-to-next-to-leading order (N$^3$LO) interactions. We are able to\nreach basis size up to $N_{max}$ = 6 for $^{18}$Ne and $N_{max}$ = 4 for the\n$^{19-24}$Ne isotopes with m-scheme dimensions up to 1.0 $\\times$ $10^9$ in\ncase of $^{24}$Ne. We observed better results for INOY interaction in terms of\nthe binding energies of ground state (g.s.), and overall all three interactions\nprovide good agreement with the experimental low-energy spectra. Our results\nfor reduced $M1$ transition strengths and magnetic moments are close to the\nexperimental values. We found that for long-range observables such as the $E2$\ntransition strengths, the electric quadrupole moments, and the point-proton\nradii ($r_p$), we need higher $N_{max}$ calculations to obtain results\ncomparable to the experimental data. We have observed almost 6 \\% increment in\nthe converged $r_p$ as we increase the model space from $N_{max}$ = 4 to\n$N_{max}$ = 6.", "category": "nucl-th" }, { "text": "Diffusion of hidden charm mesons in hadronic medium: The drag and diffusion coefficients of a hot hadronic medium have been\nevaluated by using hidden charm mesons as probes. The matrix elements for the\nevaluation of these coefficients are calculated using an effective theory as\nwell as from scattering lengths. Although the transport coefficients show a\nsignificant rise with temperature its effects on the suppression of $J/\\psi$ in\nhadronic matter is not significant.", "category": "nucl-th" }, { "text": "Quantum Fluctuations Driving the Generation and Strong Correlations of\n Fission Fragment Angular Momenta: Two critical issues in the study of the fission mechanism are how the fission\nfragment angular momenta (FFAM) develop dynamically from equilibrium and how\nthey are correlated with each other. To this end, we construct a time-dependent\ngenerator coordinate method that incorporates crucial quantum fluctuations --\nmultiple rotations, vibrations, and their couplings -- based on covariant\ndensity functional theory, providing for the first time a global, microscopic,\nand dynamical study on the FFAM distribution. The calculated probability\ndistributions of FFAM are in good agreement with the experimental measurements,\nand the sawtooth-like mass dependence of average FFAM is reproduced very well.\nIt is noteworthy to find that the quantum fluctuations drive the generation and\nchaotic evolution of FFAM during fission fragment formation and induce the\nstrong correlations of FFAM orientations at the small, medium, and large\nopening angles ($\\phi_{\\rm LH}\\approx 30^{\\rm o}$, $90^{\\rm o}$, $160^{\\rm\no}$).", "category": "nucl-th" }, { "text": "Systematics of dynamic moment of inertia in super-deformed bands in Mass\n ~150 region: An empirical semi-classical model have been proposed to investigate the\nnature of dynamic moment-of-inertia , of the super-deformed (SD) bands in\nnuclei of mass 150 region. The model incorporates an additional frequency\ndependent distortion, to the dynamic moment-of-inertia term akin to a\nvibrational component to explain the extreme spin structure of these bands.\nUsing this model two separate components to the dynamic moment of inertia,\n$\\Im^{(2)}$ have been identified for the SD band structure for the mass 150\nregion. Three distinct nature of the moment-of-inertia, also have been\nidentified using the two parameter model.", "category": "nucl-th" }, { "text": "Near-threshold $\u03b7$ production in $pp$ collisions: We study near-threshold $\\eta$ meson production in $pp$ collisions within an\neffective Lagrangian approach combined with the isobar model, by allowing for\nthe various intermediate nucleon resonances due to the $\\pi$, $\\eta$, and\n$\\rho$-meson exchanges. It is shown that the $\\rho$-meson exchange is the\ndominant excitation mechanism for these resonances, and the contribution from\nthe $N^*(1720)$ is dominant. The total cross section data can be reasonably\nreproduced, and the anisotropic angular distributions of the emitted $\\eta$\nmeson are consistent with experimental measurements. Besides, the invariant\nmass spectra of $pp$ and $p\\eta$ explain the data well at excess energy of 15\nMeV, and are basically consistent with the data at excess energy of 40 MeV.\nHowever, our model calculations cannot reasonably account for the two-peak\nstructure in the $p\\eta$ distribution at excess energies of 57 and 72 MeV,\nwhich suggests that a more complicated mechanism is needed at higher energy\nregion.", "category": "nucl-th" }, { "text": "Few-body calculations of $\u03b7$-nuclear quasibound states: We report on precise hyperspherical-basis calculations of $\\eta NN$ and $\\eta\nNNN$ quasibound states, using energy dependent $\\eta N$ interaction potentials\nderived from coupled-channel models of the $S_{11}$ $N^{\\ast}(1535)$ nucleon\nresonance. The $\\eta N$ attraction generated in these models is too weak to\ngenerate a two-body bound state. No $\\eta NN$ bound-state solution was found in\nour calculations in models where Re $a_{\\eta N}\\lesssim 1$ fm, with $a_{\\eta\nN}$ the $\\eta N$ scattering length, covering thereby the majority of\n$N^{\\ast}(1535)$ resonance models. A near-threshold $\\eta NNN$ bound-state\nsolution, with $\\eta$ separation energy of less than 1 MeV and width of about\n15 MeV, was obtained in the 2005 Green-Wycech model where Re $a_{\\eta N}\\approx\n1$ fm. The role of handling self consistently the subthreshold $\\eta N$\ninteraction is carefully studied.", "category": "nucl-th" }, { "text": "Effective forces between quantum bound states: Recent ab initio lattice studies have found that the interactions between\nalpha particles (4He nuclei) are sensitive to seemingly minor details of the\nnucleon-nucleon force such as interaction locality. In order to uncover the\nessential physics of this puzzling phenomenon without unnecessary\ncomplications, we study a simple model involving two-component fermions in one\nspatial dimension. We probe the interaction between two bound dimers for\nseveral different particle-particle interactions and measure an effective\npotential between the dimers using external point potentials which act as\nnumerical tweezers. We find that the strength and range of the local part of\nthe particle-particle interactions play a dominant role in shaping the\ninteractions between the dimers and can even determine the overall sign of the\neffective potential.", "category": "nucl-th" }, { "text": "Treatment of the proton-proton Coulomb force in proton-deuteron breakup\n Faddeev calculations: We extend our approach to incorporate the proton-proton (pp) Coulomb force\ninto the three-nucleon (3N) Faddeev calculations from elastic proton-deuteron\n(pd) scattering to the breakup process. The main new ingredient is a\n3-dimensional screened pp Coulomb t-matrix obtained by a numerical solution of\nthe 3-dimensional Lippmann-Schwinger equation. We demonstrate numerically that\nthe proton-deuteron breakup observables can be determined from the resulting\non-shell 3N amplitudes increasing the screening radius. However, contrary to\nthe pd elastic scattering, the screening limit exists only after\nrenormalisation of the pp t-matrices.", "category": "nucl-th" }, { "text": "RPA equations and the instantaneous Bethe-Salpeter equation: We give a derivation of the particle-hole RPA equations for an interacting\nmulti-fermion system by applying the instantaneous approximation to the\namputated two-fermion propagator of the system. In relativistic field theory\nthe same approximation leads from the fermion-antifermion Bethe-Salpeter\nequation to the Salpeter equation. We show that RPA equations and Salpeter\nequation are indeed equivalent.", "category": "nucl-th" }, { "text": "Quantum Monte Carlo calculations of six-quark states: The variational Monte Carlo method is used to find the ground state of six\nquarks confined to a cavity of diameter R_c, interacting via an assumed\nnon-relativistic constituent quark model (CQM) Hamiltonian. We use a flux-tube\nmodel augmented with one-gluon and one-pion exchange interactions, which has\nbeen successful in describing single hadron spectra. The variational wave\nfunction is written as a product of three-quark nucleon states with\ncorrelations between quarks in different nucleons. We study the role of quark\nexchange effects by allowing flux-tube configuration mixing. An accurate\nsix-body variational wave function is obtained. It has only ~13% rms\nfluctuation in the total energy and yields a standard deviation of ~<.1%; small\nenough to be useful in discerning nuclear interaction effects from the large\nrest mass of the two nucleons. Results are presented for three values of the\ncavity diameter, R_c=2, 4, and 6 fm. They indicate that the flux-tube model\nHamiltonian with gluon and pion exchange requires revisions in order to obtain\nagreement with the energies estimated from realistic two-nucleon interactions.\nWe calculate the two-quark probability distribution functions and show how they\nmay be used to study and adjust the model Hamiltonian.", "category": "nucl-th" }, { "text": "Neutron Anomalous Magnetic Moment in Dense Magnetized Systems: In this work, we calculate the neutron anomalous magnetic moment supposing\nthat this value can depend on the density and magnetic field of system. We\nemploy the lowest order constraint variation (LOCV) method and $AV_{18}$\nnuclear potential to calculate the medium dependency of the neutron anomalous\nmagnetic moment. It is confirmed that the neutron anomalous magnetic moment\nincreases by increasing the density, while it decreases as the magnetic field\ngrows. The energy and equation of state for the system have also been\ninvestigated.", "category": "nucl-th" }, { "text": "Rotation and alignment of high-$j$ orbitals in transfermium nuclei: The structure of nuclei with $Z\\sim100$ is investigated systematically by the\nCranked Shell Model (CSM) with pairing correlations treated by a\nParticle-Number Conserving (PNC) method. In the PNC method, the particle number\nis conserved and the Pauli blocking effects are taken into account exactly. By\nfitting the experimental single-particle spectra in these nuclei, a new set of\nNilsson parameters ($\\kappa$ and $\\mu$) is proposed. The experimental kinematic\nmoments of inertia and the band-head energies are reproduced quite well by the\nPNC-CSM calculations. The band crossing, the effects of high-$j$ intruder\norbitals and deformation are discussed in detail.", "category": "nucl-th" }, { "text": "Interference Effect Between Neutron Direct and Resonance Capture\n Reactions For Neutron-Rich Nuclei: Interference effect of neutron capture cross section between the compound and\ndirect processes is investigated. The compound process is calculated by\nresonance parameters and the direct process by the potential mode. The\ninterference effect is tested for neutron-rich $^{82}$Ge and $^{134}$Sn nuclei\nrelevant to $r$-process and light nucleus $^{13}$C which is neutron poison in\nthe $s$-process and produces long-lived radioactive nucleus $^{14}$C\n($T_{1/2}=5700$ y). The interference effects in those nuclei are significant\naround resonances, and low energy region if $s$-wave neutron direct capture is\npossible. Maxwellian averaged cross sections at $kT=30$ and $300$ keV are also\ncalculated, and the interference effect changes the Maxwellian averaged capture\ncross section largely depending on resonance position.", "category": "nucl-th" }, { "text": "Parity Mixed Doublets in A = 36 Nuclei: The $\\gamma$-circular polarizations ($P_{\\gamma}$) and asymmetries\n($A_{\\gamma}$) of the parity forbidden M1 + E2 $\\gamma$-decays: $^{36}Cl^{\\ast}\n(J^{\\pi} = 2^{-}; T = 1; E_{x} = 1.95 $ MeV) $\\rightarrow$ $^{36}Cl (J^{\\pi} =\n2^{+}; T = 1; g.s.)$ and $^{36}Ar^{\\ast} (J^{\\pi} = 2^{-}; T = 0; E_{x} = 4.97\n$ MeV) $\\rightarrow$ $^{36}Ar^{\\ast} (J^{\\pi} = 2^{+}; T = 0; E_{x} = 1.97 $\nMeV) are investigated theoretically. We use the recently proposed\nWarburton-Becker-Brown shell-model interaction. For the weak forces we discuss\ncomparatively different weak interaction models based on different assumptions\nfor evaluating the weak meson-hadron coupling constants. The results determine\na range of $P_{\\gamma}$ values from which we find the most probable values:\n$P_{\\gamma}$ = $1.1 \\cdot 10^{-4}$ for $^{36}Cl$ and $P_{\\gamma}$ = $3.5 \\cdot\n10^{-4}$ for $^{36}Ar$.", "category": "nucl-th" }, { "text": "Skyrme interaction to second order in nuclear matter: Based on the phenomenological Skyrme interaction various density-dependent\nnuclear matter quantities are calculated up to second order in many-body\nperturbation theory. The spin-orbit term as well as two tensor terms contribute\nat second order to the energy per particle. The simultaneous calculation of the\nisotropic Fermi-liquid parameters provides a rigorous check through the\nvalidity of the Landau relations. It is found that published results for these\nsecond order contributions are incorrect in most cases. In particular,\ninterference terms between $s$-wave and $p$-wave components of the interaction\ncan contribute only to (isospin or spin) asymmetry energies. Even with nine\nadjustable parameters, one does not obtain a good description of the empirical\nnuclear matter saturation curve in the low density region $0<\\rho<2\\rho_0$. The\nreason for this feature is the too strong density-dependence $\\rho^{8/3}$ of\nseveral second-order contributions. The inclusion of the density-dependent term\n${1\\over 6}t_3 \\rho^{1/6}$ is therefore indispensable for a realistic\ndescription of nuclear matter in the Skyrme framework.", "category": "nucl-th" }, { "text": "Missing Resonances in Kaon Photoproduction on the Nucleon: New kaon photoproduction data on a proton, gamma + p --> K+ + Lambda, are\nanalyzed using a multipole approach. The background terms are given in terms of\ngauge invariant, crossing symmetric, Born diagrams with hadronic form factors,\nwhile the resonances are parameterized using Breit-Wigner forms. Preliminary\nresults suggest a number of new resonances, as predicted by many quark model\nstudies. A comparison between the extracted multipoles and those obtained from\nKAON-MAID is presented.", "category": "nucl-th" }, { "text": "The Nuclear Reactions in Standard BBN: Nowadays, the Cosmic Microwave Background (CMB) anisotropies studies\naccurately determine the baryon fraction omega_b, showing an overall and\nstriking agreement with previous determinations of omega_b obtained from Big\nBang Nucleosynthesis (BBN). However, a deeper comparison of BBN predictions\nwith the determinations of the primordial light nuclides abundances shows\nslight tensions, motivating an effort to further improve the accuracy of\ntheoretical predictions, as well as to better evaluate systematics in both\nobservations and nuclear reactions measurements. We present some results of an\nimportant step towards an increasing precision of BBN predictions, namely an\nupdated and critical review of the nuclear network, and a new protocol to\nperform the nuclear data regression.", "category": "nucl-th" }, { "text": "Perturbative accelerating solutions of relativistic hydrodynamics: In ultra-relativistic collisions of heavy ions, the strongly interacting\nQuark Gluon Plasma (sQGP) is created. The fluid nature of the sQGP was one of\nthe important discoveries of high energy heavy ion physics in the last decades.\nHenceforth the explosion of this matter may be described by hydrodynamical\nmodels. Besides numerical simulations, it is important to study the analytic\nsolutions of the equations of hydrodynamics, as these enable us to understand\nthe connection of the final and initial states better. In this paper we present\na perturbative, accelerating solution of relativistic hydrodynamics, on top of\na known class of solutions describing Hubble-expansion. We describe the\nproperties of this class of perturbative solutions, and investigate a few\nselected solutions in detail.", "category": "nucl-th" }, { "text": "Studies of quasiclassical approach applicability to true three-body\n decays: Within the hyperspherical harmonics approach the three-body problem is\nreduced to a motion of one effective particle in a \"strongly deformed\" field,\nwhich is described in coupled-channel formalism. This method is especially\nsuited to studies of phenomena characterized by genuine three-body dynamics,\ne.g. Borromean haloes and true three-body decays. The reduction of the\nhyperspherical equations set to a single-channel Schr\\\"odinger equation\nprovides the basis for the use of the standard quasiclassical expression for\ncalculations of widths for true three-body decays. We demonstrate that the\nquasiclassical approach by itself is quite precise in application to typical\nprofiles of the three-body effective potentials. However, the reduction to\nsingle-channel formalism leads to significant overestimation of the two-proton\nwidth $\\Gamma_{2p}$. This is demonstrated by the example of the $^{17}$Ne first\nexcited $3/2^-$ state decay, questioning, however, the applicability of such an\napproximation in general.", "category": "nucl-th" }, { "text": "The entropy puzzle and the quark combination model: We use two available methods, the Duhem-Gibbs relation and the entropy\nformula in terms of particle phase space distributions, to calculate the\nentropy in a quark combination model. The entropy of the system extracted from\nthe Duhem-Gibbs relation is found to increase in hadronization if the average\ntemperature of the hadronic phase is lower than that of the quark phase. The\nincrease of the entropy can also be confirmed from the entropy formula if the\nvolume of the hadronic phase is larger than 2.5-3.0 times that of the quark\nphase. So whether the entropy increases or decreases during combination depends\non the temperature before and after combination and on how much expansion the\nsystem undergoes during combination. The current study provides an example to\nshed light on the entropy issue in the quark combination model.", "category": "nucl-th" }, { "text": "Chiral effective field theory for nuclear matter: We report on the recent developments of a new effective field theory for\nnuclear matter [1,2,3]. We present first the nuclear matter chiral power\ncounting that takes into account both short-- and long--range inter-nucleon\ninteractions. It also identifies non-perturbative strings of diagrams, related\nto the iteration of nucleon-nucleon interactions, which have to be re-summed.\nThe methods of unitary chiral perturbation theory has been shown to be a useful\ntool in order to perform those resummations. Results up to next-to-leading\norder for the ground state energy per particle of nuclear matter, the in-medium\nchiral quark condensate and pion self-energy are discussed.", "category": "nucl-th" }, { "text": "The sixth order cumulant of net-proton number in Binomial distribution\n at $\\sqrt{s_{NN}} = $ 200 GeV: It is proposed that ratios of the sixth order to the second order cumulant\n($C_6/C_2$) of conserved quantities are sensitive to the chiral crossover\ntransition. Recently, the negative $C_6/C_2$ was obtained both in theoretical\nLattice QCD and experiments at $\\sqrt{s_{NN}} = $ 200 GeV. In this study, we\ninvestigate the behavior of net-proton $C_6/C_2$ in statistical Binomial\ndistribution (BD) at $\\sqrt{s_{NN}} = $ 200 GeV in Au + Au collisions. With the\nBD parameters extracted from RHIC/STAR, it is found that $C_6/C_2$ can be\nnegative. Furthermore, the obtained $C_6/C_2$ becomes smaller when applying the\nsame magnitude of experimental statistics and calculation method to\nsimulations. In 0-10\\% centrality, there is a significant difference between\nthe simulated result and theoretical expectation. Based on the extracted\nparameters and experimentally collected statistics, the baseline of net-proton\n$C_6/C_2$ in BD is presented.", "category": "nucl-th" }, { "text": "Probing the multi-scale dynamical interaction between heavy quarks and\n the QGP using JETSCAPE: The dynamics of shower development for a jet traveling through the QGP\ninvolves a variety of scales, one of them being the heavy quark mass. Even\nthough the mass of the heavy quarks plays a subdominant role during the high\nvirtuality portion of the jet evolution, it does affect longitudinal drag and\ndiffusion, stimulating additional radiation from heavy quarks. These emissions\npartially compensate the reduction in radiation from the dead cone effect. In\nthe lower virtuality part of the shower, when the mass is comparable to the\ntransverse momenta of the partons, scattering and radiation processes off heavy\nquarks differ from those off light quarks. All these factors result in a\ndifferent nuclear modification factor for heavy versus light flavors and thus\nfor heavy-flavor tagged jets.\n In this study, the heavy quark shower evolution and the fluid dynamical\nmedium are modeled on an event by event basis using the JETSCAPE Framework. We\npresent a multi-stage calculation that explores the differences between various\nheavy quark energy-loss mechanisms within a realistically expanding quark-gluon\nplasma (QGP). Inside the QGP, the highly virtual and energetic portion of the\nshower is modeled using the MATTER generator, while the LBT generator models\nthe showers induced by energetic and close-to-on-shell heavy quarks.\nEnergy-momentum exchange with the medium, essential for the study of jet\nmodification, proceeds using a weak coupling recoil approach. The JETSCAPE\nframework allows for transitions, on the level of individual partons, from one\nenergy-loss prescription to the other depending on the parton's energy and\nvirtuality and the local density. This allows us to explore the effect and\ninterplay between the different regimes of energy loss on the propagation and\nradiation from hard heavy quarks in a dense medium.", "category": "nucl-th" }, { "text": "Equivalence between first-order causal and stable hydrodynamics and\n Israel-Stewart theory for boost-invariant systems with a constant relaxation\n time: We show that the recently formulated causal and stable first-order\nhydrodynamics has the same dynamics as Israel-Stewart theory for\nboost-invariant, Bjorken expanding systems with a conformal equation of state\nand a regulating sector determined by a constant relaxation time. In this case,\nthe general solution of the new first-order formulation can be determined\nanalytically.", "category": "nucl-th" }, { "text": "The baryon number two system in the Chiral Soliton Model: We study the interaction between two B = 1 states in a Chiral Soliton Model\nwhere baryons are described as non-topological solitons. By using the hedgehog\nsolution for the B = 1 states we construct three possible B = 2 configurations\nto analyze the role of the relative orientation of the hedgehog quills in the\ndynamics. The strong dependence of the intersoliton interaction on these\nrelative orientations reveals that studies of dense hadronic matter using this\nmodel should take into account their implications.", "category": "nucl-th" }, { "text": "Hadronic resonance production and interaction in p-Pb collisions at LHC\n energies in EPOS3: Using the EPOS3 model with UrQMD to describe the hadronic phase, we study the\nproduction of short-lived hadronic resonances and the modification of their\nyields and $p_{T}$ spectra in p-Pb collisions at $\\sqrt{s_{NN}}$ = 5.02 TeV.\nHigh-multiplicity p-Pb collisions exhibit similar behavior to mid-peripheral\nPb-Pb collisions at LHC energies, and we find indications of a short-lived\nhadronic phase in p-Pb collisions that can modify resonance yields and $p_{T}$\nspectra through scattering processes. The evolution of resonance production is\ninvestigated as a function of the system size, which is related to the lifetime\nof the hadronic phase, in order to study the onset of collective effects in\np-Pb collisions. We also study hadron production separately in the core and\ncorona parts of these collisions, and explore how this division affects the\ntotal particle yields as the system size increases.", "category": "nucl-th" }, { "text": "Perspectives on few-body cluster structures in exotic nuclei: It is a fascinating phenomenon in nuclear physics that states with a\npronounced few-body structure can emerge from the complex dynamics of many\nnucleons. Such halo or cluster states often appear near the boundaries of\nnuclear stability. As such, they are an important part of the experimental\nprogram beginning at the Facility for Rare Isotope Beams (FRIB). A concerted\neffort of theory and experiment is necessary both to analyze experiments\ninvolving effective few-body states, as well as to constrain and refine\ntheories of the nuclear force in light of new data from these experiments. As a\ncontribution to exactly this effort, this paper compiles a collection of\n``perspectives'' that emerged out of the Topical Program ``Few-body cluster\nstructures in exotic nuclei and their role in FRIB experiments'' that was held\nat FRIB in August 2022 and brought together theorists and experimentalists\nworking on this topic.", "category": "nucl-th" }, { "text": "Elliptic flow from a parton cascade: The dependence of elliptic flow at RHIC energies on the effective parton\nscattering cross section is calculated using the ZPC parton cascade model. We\nshow that the v_2 measure of elliptic flow saturates early in the evolution\nbefore the hadronization transition to a rather large value ~0.05-0.15 as\n\\sigma_g varies from 2-10 mb and thus is a sensitive probe of the dynamics in\nthe plasma phase.", "category": "nucl-th" }, { "text": "Mean field approach to flavor susceptibilities with a vector interaction: We show that flavor diagonal and off-diagonal susceptibilities of light\nquarks at vanishing chemical potential can be calculated consistently assuming\nthe baryon density and isospin density dependence of QCD to be expressed by a\nvector-isoscalar and a vector-isovector coupling, respectively. At the mean\nfield level, their expression depends only on the effective medium-dependent\ncouplings and quark thermodynamic potential. The strength of the couplings can\nbe then estimated from the model using lattice QCD data as an input.", "category": "nucl-th" }, { "text": "Relativistic Approach to Isoscalar Giant Resonances in 208Pb: We calculate the longitudinal response of 208Pb using a relativistic\nrandom-phase approximation to three different parameterizations of the Walecka\nmodel with scalar self-interactions. From a nonspectral calculation of the\nresponse-that automatically includes the mixing between positive- and\nnegative-energy states-we extract the distribution of strength for the\nisoscalar monopole, dipole, and high-energy octupole resonances. We employ a\nconsistent formalism that uses the same interaction in the calculation of the\nground state as in the calculation of the response. As a result, the\nconservation of the vector current is strictly maintained throughout the\ncalculation. Further, at small momentum transfers the spurious dipole\nstrength-associated with the uniform translation of the center-of-mass-gets\nshifted to zero excitation energy and is cleanly separated from the sole\nremaining physical fragment located at an excitation energy of about 24 MeV; no\nadditional dipole strength is observed. The best description of the collective\nmodes is obtained using a ``soft'' parameterization having a compression\nmodulus of K=224 MeV.", "category": "nucl-th" }, { "text": "Nuclear medium effects in $\u03bd/\\bar\u03bd$-A DIS: Nuclear medium effects in the weak structure functions $F_2(x,Q^2)$ and\n$F_3(x,Q^2)$ have been studied for deep inelastic neutrino/antineutrino\nreactions in iron nucleus by taking into account Fermi motion, binding, pion\nand rho meson cloud contributions, target mass correction, shadowing and\nanti-shadowing corrections. The calculations have been performed in a local\ndensity approximation using relativistic nuclear spectral functions which\ninclude nucleon correlations. Using these structure functions we have obtained\nthe ratio $R_{F2,F3}^A(x,Q^2)= \\frac{2F_{2,3}^A(x,Q^2)}{AF_{2,3}^D(x,Q^2)}$,\nthe differential scattering cross section $\\frac{1}{E}\\frac{d^2\\sigma}{dxdy}$\nand the total scattering cross section $\\sigma$. The results of our numerical\ncalculations in $^{56}Fe$ are compared with the experimental results of NuTeV\nand CDHSW collaborations.", "category": "nucl-th" }, { "text": "Probing Vector Mesons in Deuteron Break-up Reactions: We study vector meson photoproduction from the deuteron at high momentum\ntransfer, accompanied by break-up of the deuteron into a proton and neutron.\nThe large $-t$ involved allows one of the nucleons to be identified as struck,\nand the other as a spectator to the $\\gamma N\\rightarrow VN$ subprocess.\nCorrections to the plane wave impulse approximation involve final state\ninteractions (FSIs) between the struck nucleon or the vector meson, either of\nwhich is energetic, with the slow spectator nucleon. In this regime, the\neikonal approximation is valid, so is employed to calculate the cross-section\nfor the reaction. Due to the high-energy nature of the FSIs, the maxima of the\nrescatterings are located at nearly transverse directions of the fast hadrons.\nThis results in two peaks in the angular distribution of the spectator nucleon,\neach corresponding to either the $V$-$N$ or the $p$-$n$ rescattering. The\n$V$-$N$ peak provides a new means of probing the $V$-$N$ interaction. This is\nchecked for near-threshold $\\phi$ and $J/\\Psi$ photoproduction reactions which\ndemonstrate that the $V$-$N$ peak can be used to extract the largely unknown\namplitudes of $\\phi$-$N$ and $J/\\Psi$-$N$ interactions.\n Two additional phenomena are observed when extending the calculation of\n$J/\\Psi$ photoproduction to the sub-threshold and high-energy domains. In the\nfirst case we observe overall suppression of FSI effects due to a restricted\nphase space for sub-threshold production in the rescattering amplitude. In the\nsecond, we observe cancellation of the $V$-$N$ rescattering amplitudes for\nvector mesons produced off of different nucleons in the deuteron.", "category": "nucl-th" }, { "text": "Resonances in the three-neutron system: A study of 3-body resonances has been performed in the framework of\nconfiguration space Faddeev equations. The importance of keeping a sufficient\nnumber of terms in the asymptotic expansion of the resonance wave function is\npointed out. We investigated three neutrons interacting in selected force\ncomponents taken from realistic nn forces.", "category": "nucl-th" }, { "text": "Faddeev calculation of 6 He Lambda Lambda using SU_6 quark-model\n baryon-baryon interactions: Quark-model hyperon-nucleon and hyperon-hyperon interactions by the\nKyoto-Niigata group are applied to the two-Lambda plus alpha system in a new\nthree-cluster Faddeev formalism using two-cluster resonating-group method\nkernels. The model fss2 gives a reasonable two-Lambda separation energy Delta\nB_{Lambda Lambda}=1.41 MeV, which is consistent with the recent empirical\nvalue, Delta B^{exp}_{Lambda Lambda}=1.01 +/- 0.20 MeV, deduced from the Nagara\nevent. Some important effects that are not taken into account in the present\ncalculation are discussed.", "category": "nucl-th" }, { "text": "Meson elastic and transition form factors: The Dyson-Schwinger equations of QCD, truncated to ladder-rainbow level, are\nused to calculate meson form factors in impulse approximation. The infrared\nstrength of the ladder-rainbow kernel is described by two parameters fitted to\nthe chiral condensate and f_pi; the ultraviolet behavior is fixed by the QCD\nrunning coupling. This obtained elastic form factors F_pi(Q^2) and F_K(Q^2)\nagree well with the available data. We also calculate the rho to pi gamma and\nK* to K gamma transition form factors, which are useful for meson-exchange\nmodels.", "category": "nucl-th" }, { "text": "Gaussian matrix elements in a cylindrical harmonic oscillator basis: We derive a formalism, the separation method, for the efficient and accurate\ncalculation of two-body matrix elements for a Gaussian potential in the\ncylindrical harmonic-oscillator basis. This formalism is of critical importance\nfor Hartree-Fock and Hartree-Fock-Bogoliubov calculations in deformed nuclei\nusing realistic, finite-range effective interactions between nucleons. The\nresults given here are also relevant for microscopic many-body calculations in\natomic and molecular physics, as the formalism can be applied to other types of\ninteractions beyond the Gaussian form. The derivation is presented in great\ndetail to emphasize the methodology, which relies on generating functions. The\nresulting analytical expressions for the Gaussian matrix elements are checked\nfor speed and accuracy as a function of the number of oscillator shells and\nagainst direct numerical integration.", "category": "nucl-th" }, { "text": "Event-by-event pT fluctuations and multiparticle clusters in\n relativistic heavy-ion collisions: We explore the dependence of the pT correlations in the event-by-event\nanalysis of relativistic heavy-ion collisions at RHIC made recently by the\nPHENIX and STAR Collaborations. We point out that the observed scaling of\nstrength of dynamical fluctuations with the inverse number of particles can be\nnaturally explained by the formation of clusters. We argue that the large\nmagnitude of the measured covariance implies that the clusters contain at least\nseveral particles. We also discuss whether the clusters may originate from\njets. In addition, we provide numerical estimates of correlations coming from\nresonance decays and thermal clusters.", "category": "nucl-th" }, { "text": "Pasta structures in compact stars: We review our recent works about ``pasta'' structures following the\nfirst-order phase transition in dense matter, which correspond to the\nstructured mixed phases with geometrical symmetries. Three kinds of phase\ntransitions at different density ranges are examined as the stages of pasta\nstructures: liquid-gas phase transition at subnuclear density, kaon\ncondensation and hadron-quark phase transition at high density. Charge density\nas well as particle density is non-uniform there. A consistent treatment of the\nCoulomb potential and the particle densities is presented and a peculiar role\nof the Coulomb potential is elucidated: the physical picture of the Maxwell\nconstruction will be effectively recovered. It largely influences the density\nregime of pasta structures by the charge screening effect.", "category": "nucl-th" }, { "text": "Calculation of Doublet Capture Rate for Muon Capture in Deuterium within\n Chiral Effective Field Theory: The doublet capture rate of the negative muon capture in deuterium is\ncalculated employing the nuclear wave functions generated from accurate\nnucleon-nucleon potentials constructed at next-to-next-to-next-to-leading order\nof heavy-baryon chiral perturbation theory and the weak meson exchange current\noperator derived within the same formalism. All but one of the low-energy\nconstants that enter the calculation were fixed from pion-nucleon and\nnucleon-nucleon scattering data. The low-energy constant d^R (c_D), which\ncannot be determined from the purely two-nucleon data, was extracted recently\nfrom the triton beta-decay and the binding energies of the three-nucleon\nsystems. The calculated values of the doublet capture rates show a rather large\nspread for the used values of the d^R. Precise measurement of the doublet\ncapture rate in the future will not only help to constrain the value of d^R,\nbut also provide a highly nontrivial test of the nuclear chiral EFT framework.\nBesides, the precise knowledge of the constant d^R will allow for consistent\ncalculations of other two-nucleon weak processes, such as proton-proton fusion\nand solar neutrino scattering on deuterons, which are important for\nastrophysics.", "category": "nucl-th" }, { "text": "Correlations between neutrons and protons near Fermi surface and\n $Q_\u03b1$ of super-heavy nuclei: The shell corrections and shell gaps in nuclei are systematically studied\nwith the latest Weizs\\\"acker-Skyrme (WS4) mass model. We find that most of\nasymmetric nuclei with (sub)-shell closures locate along the shell stability\nline (SSL), $N=1.37Z+13.5$, which might be due to a strong correlation between\nneutrons and protons near Fermi surface. The double magicity of nuclei\n$^{46}$Si and $^{78}$Ni is predicted according to the corresponding shell gaps,\nshell corrections and nuclear deformations. The unmeasured super-heavy nuclei\n$^{296}$118 and $^{298}$120, with relatively large shell gaps and shell\ncorrections, also locate along the SSL, whereas the traditional magic nucleus\n$^{298}$Fl evidently deviates from the line. The $\\alpha$-decay energies of\nsuper-heavy nuclei with $Z=113-126$ are simultaneously investigated by using\nthe WS4 model together with the radial basis function corrections. For\nsuper-heavy nuclei with large shell corrections, the smallest $\\alpha$-decay\nenergy for elements $Z=116$, 117 and 118 in their isotope chains locates at\n$N=178$ rather than $184$.", "category": "nucl-th" }, { "text": "Correlations and Clustering in Dilute Matter: Nuclear systems are treated within a quantum statistical approach.\nCorrelations and cluster formation are relevant for the properties of warm\ndense matter, but the description is challenging and different approximations\nare discussed. The equation of state, the composition, Bose condensation of\nbound fermions, the disappearance of bound states at increasing density because\nof Pauli blocking are of relevance for different applications in astrophysics,\nheavy ion collisions, and nuclear structure.", "category": "nucl-th" }, { "text": "The One-Boson-Exchange Potential Model Approach: A review is given of the present situation in YN scattering. Special\nattention is given to the handling of SU(3) in the various meson exchanges. The\nimportance of the almost always ignored contribution of the Pomeron is\nreiterated.", "category": "nucl-th" }, { "text": "Limiting Fragmentation in a Thermal Model with Flow: The property of limiting fragmentation of various observables such as\nrapidity distributions ($dN/dy$), elliptic flow ($v_{2}$), average transverse\nmomentum ($\\langle p_{T} \\rangle$) etc. of charged particles is observed when\nthey are plotted as a function of rapidity ($y$) shifted by the beam rapidity\n($y_{beam}$) for a wide range of energies from AGS to RHIC. Limiting\nfragmentation (LF) is a well studied phenomenon as observed in various\ncollision energies and colliding systems experimentally. It is very interesting\nto verify this phenomenon theoretically. We study such a phenomenon for pion\nrapidity spectra using our hydrodynamic-like model where the collective flow is\nincorporated in a thermal model in the longitudinal direction. Our findings\nadvocate the observation of extended longitudinal scaling in the rapidity\nspectra of pions from AGS to lower RHIC energies, while it is observed to be\nviolated at top RHIC and LHC energies. Prediction of LF hypothesis for Pb+Pb\ncollisions at $\\sqrt{s_{NN}}$=5.02 TeV is given.", "category": "nucl-th" }, { "text": "NN correlations and final-state interactions in (e,e'NN) reactions: After a brief overview of relevant studies on one-nucleon knockout showing\nthe importance of quantitatively understanding the origin of the quenched\nspectroscopic factors extracted from data, attention is focussed on two-nucleon\nemission as a suitable tool to investigate nucleon-nucleon correlations inside\ncomplex nuclei. In particular, direct (e,e$'$pp) and (e,e$'$pn) reactions are\ndiscussed, and the role of final-state interactions is studied. The influence\nof the mutual interaction between the two outgoing nucleons is shown to depend\non the kinematics and on the type of the considered reaction.", "category": "nucl-th" }, { "text": "Nature of particles azimuthal anisotropy at low and high transverse\n momenta in ultrarelativistic A+A collisions: LHC data on the correlations of the elliptic flow $v_2$ of particles at low\nand high transverse momenta $p_T$ from Pb+Pb collisions at center-of-mass\nenergy per nucleon pair $\\sqrt{s_{NN}} = 5.02$ TeV are analyzed in the\nframework of the HYDJET++ model. This model includes soft and hard components\nwhich allows to describe the region of both low and high transverse momenta.\nThe origin of $v_2$ values in different $p_T$ regions is investigated at\ndifferent centralities. It is shown that the experimentally observed\ncorrelations between $v_2$ at low and high $p_T$ in peripheral lead-lead\ncollisions is due to correlation of particles in jets.", "category": "nucl-th" }, { "text": "High-precision nuclear forces from chiral EFT: State-of-the-art,\n challenges and outlook: We review a new generation of nuclear forces derived in chiral effective\nfield theory using the recently proposed semilocal regularization method. We\noutline the conceptual foundations of nuclear chiral effective field theory,\ndiscuss all steps needed to compute nuclear observables starting from the\neffective chiral Lagrangian and consider selected applications in the two- and\nfew-nucleon sectors. We highlight key challenges in developing high-precision\ntree-body forces, such as the need to maintain consistency between two- and\nmany-body interactions and constraints placed by the chiral and gauge\nsymmetries after regularization.", "category": "nucl-th" }, { "text": "Conserved Charge Susceptibilities in a Chemically Frozen Hadronic Gas: In a hadronic gas with three conserved charges (electric charge, baryon\nnumber, and strangeness) we employ the hadron resonance gas model to compute\nboth diagonal and off-diagonal susceptibilities. We model the effect of\nchemical freeze-out in two ways: one in which all particle numbers are\nconserved below the chemical freeze-out temperature and one which takes into\naccount resonance decays. We then briefly discuss possible implications these\nresults may have on two active areas of research, hydrodynamic fluctuations and\nthe search for the QCD critical point.", "category": "nucl-th" }, { "text": "Current Status of Nuclear Physics Research: In this review we discuss the current status of research in nuclear physics\nwhich is being carried out in different centers in the World. For this purpose\nwe supply a short account of the development in the area which evolved over the\nlast 9 decades, since the discovery of the neutron. The evolution of the\nphysics of the atomic nucleus went through many stages as more data become\navailable. We briefly discuss models introduced to discern the physics behind\nthe experimental discoveries, such as the shell model, the collective model,\nthe statistical model, the interacting boson model, etc., some of these models\nmay be seemingly in conflict with each other, but this was shown to be only\napparent.\n The richness of the ideas and abundance of theoretical models attests to the\nimportant fact that the nucleus is a really singular system in the sense that\nit evolves from two-body bound states such as the deuteron, to few-body bound\nstates, such as $^4$He, $^7$Li, $^9$Be etc. and up the ladder to heavier bound\nnuclei containing up to more than 200 nucleons. Clearly statistical mechanics\ndoes not work for such finite system, neither does other theories applicable to\ncondensed matter systems. The richness of nuclear physics stems from these\nrestrictions. New theories and models are presently being developed. Theories\nof the structure and reactions of neutron-rich and proton-rich nuclei, called\nexotic nuclei, halo nuclei, or Borromean nuclei deal with the wealth of\nexperimental data available in the last 35 years. Further, nuclear astrophysics\nand stellar and Big Bang nucleosynthesis have become a more mature subject. Due\nto limited space, this review only covers a few selected topics, mainly those\nwith which the authors have worked with.", "category": "nucl-th" }, { "text": "Medium polarization and finite size effects on the superfluidity of the\n inner crust of neutron stars: The 1S0 pairing gap associated with the inner crust of a neutron star is\ncalculated, taking into account the coexistence of the nuclear lattice with the\nsea of free neutrons (finite size effects), as well as medium polarization\neffects associated with the exchange of density and spin fluctuations. Both\neffects are found to be important and to lead to an overall quenching of the\npairing gap. This result, whose quantitative value is dependent on the\neffective interaction used to generate the single-particle levels, is a\nconsequence of the balance between the attractive (repulsive) induced\ninteraction arising from the exchange of density (spin) modes, balance which in\nturn is influenced by the presence of the protons and depends on the\nsingle-particle structure of the system.", "category": "nucl-th" }, { "text": "Quarkyonic Percolation and deconfinement at finite density and number of\n colors: We examine the interplay between the percolation and the deconfinement phase\ntransitions of Yang-Mills matter at finite temperature, quark chemical\npotential $\\mu_Q$ and number of colors $N_c$. We find that, whereas the\ncritical $N_c$ for percolation goes down with density, the critical $N_c$ for\nconfinement generally goes up. Because of this, Yang-Mills matter falls into\ntwo qualitatively different regimes: the \"low-$N_c$ limit\", where percolation\ndoes not occur because matter deconfines before it percolates, and the\nhigh-$N_c$ limit, where there are three distinct phases characterizing\nYang-Mills matter at finite temperature and density: confined, deconfined and\nconfined but percolating matter. The latter can be thought of as the recently\nconjectured \"quarkyonic phase\". We attempt to estimate the critical $N_c$, to\nsee if the percolating phase can occur in our world. We find that, while\npercolation will not occur at normal nuclear density as in the large-$N_c$\nlimit, a sliver of the phase diagram in $N_c$, energy density and baryonic\ndensity where percolation occurs while confinement persists is possible. We\nconclude by speculating on the phenomenological properties of such percolating\n\"quarkyonic\" matter, suggest avenues to study it quantitatively, and look for\nit in experiment.", "category": "nucl-th" }, { "text": "The position of the quasielastic peak and electron Coulomb distortion in\n (e,e') scattering: The position of the quasielastic peak for (e,e') scattering off 208-Pb\nextracted from a selected data set measured at Saclay is related to a heuristic\ntheoretical description. An analysis of the data shows that the peak position\ncan be described very accurately by a simple equation in the relevant kinematic\nregion where a pronounced peak is observable. The simple findings result in a\nconcluding comment related to recent calculations concerning the Coulomb\ndistortion in (e,e') scattering for heavy nuclei.", "category": "nucl-th" }, { "text": "$\\mathbf{D_s}$-Meson as Quantitative Probe of Diffusion and\n Hadronization in Nuclear Collisions: The modifications of $D_s$-meson spectra in ultrarelativistic heavy-ion\ncollisions are identified as a quantitative probe of key properties of the hot\nnuclear medium. This is enabled by the unique valence-quark content of the\n$D_s$=$c\\bar{s}$ which couples the well-known strangeness enhancement with the\ncollective-flow pattern of primordially produced charm quarks. We employ a\nconsistent strong-coupling treatment with hydrodynamic bulk evolution and\nnonperturbative $T$-matrix interactions for both heavy-quark diffusion and\nhadronization in the Quark-Gluon Plasma (QGP). A large enhancement of the $D_s$\nnuclear modification factor ($R_{AA}$) at RHIC is predicted, with a remarkable\nmaximum of $\\sim$1.5-1.8 at transverse momenta around 2 GeV/$c$. We show this\nto be a direct consequence of the strong coupling of the heavy quarks to the\nQGP and their hadronization via coalescence with strange quarks. We furthermore\nintroduce the effects of diffusion in the hadronic phase and suggest that an\nincrease of the $D$-meson elliptic flow compared to the $D_s$ can disentangle\nthe transport properties of hadronic and QGP liquids.", "category": "nucl-th" }, { "text": "Deformation properties with a finite range simple effective interaction: Deformed and spherical even-even nuclei are studied using a finite range\nsimple effective interaction within the Hartree-Fock-Bogoliubov mean field\napproach. Different parameter sets of the interaction, corresponding to\ndifferent incompressibility, are constructed by varying the exponent gamma of\nthe density in the traditional density-dependent term. Ten of the twelve\nparameters of these interactions are determined from properties of asymmetric\nnuclear matter and spin polarized pure neutron matter. The two remaining\nparameters are fitted to reproduce the experimental binding energies known in\n620 even-even nuclei using several variants of the rotational energy\ncorrection. The rms deviations for the binding energy depend on the value of\ngamma and the way the rotational energy correction is treated but they can be\nas low as 1.56 MeV, a value competitive with other renowned effective\ninteractions of Skyrme and Gogny type. Charge radii are compared to the\nexperimental values of 313 even-even nuclei and the rms deviation is again\ncomparable and even superior to the one of popular Skyrme and Gogny forces.\nEmphasis is given to the deformation properties predicted with these\ninteractions by analyzing the Potential Energy Surfaces for several well\ndeformed nuclei and the fission barriers of some nuclei. Comparison of the\nresults with the experimental information, where available, as well as with the\nresults of the Gogny D1S force shows satisfactory agreement.", "category": "nucl-th" }, { "text": "Neutrino emission from Cooper pairs at finite temperatures: A brief review is given of the current state of the problem of neutrino pair\nemission through neutral weak currents caused by the Cooper pairs breaking and\nformation (PBF) in superfluid baryon matter at thermal equilibrium. The cases\nof singlet-state pairing with isotropic superfluid gap and spin-triplet pairing\nwith anisotropic gap are analyzed with allowance for the anomalous weak\ninteractions caused by superfluidity. It is shown that taking into account the\nanomalous weak interactions in both the vector and axial channels is very\nimportant for a correct description of neutrino energy losses through the PBF\nprocesses. The anomalous contributions lead to an almost complete suppression\nof the PBF neutrino emission in spin-singlet superfluids and strong reduction\nof the PBF neutrino losses in the spin-triplet superfluid neutron matter, which\nconsiderably slows down the cooling rate of neutron stars with superfluid\ncores.", "category": "nucl-th" }, { "text": "Effect of color superconductivity on the mass of hybrid neutron stars in\n an effective model with pQCD asymptotics: The effective cold quark matter model by Alford, Braby, Paris and Reddy\n(ABPR) is used as a tool for discussing the effect of the size of the pairing\ngap in three-flavor (CFL) quark matter on the maximum mass of hybrid neutron\nstars (NSs). This equation of state (EOS) has three parameters which we suggest\nto determine by comparison with a nonlocal NJL model of quark matter in the\nnonperturbative domain. We show that due to the momentum dependence of the\npairing which is induced by the nonlocality of the interaction, the effective\ngap parameter in the EOS model is well approximated by a constant value\ndepending on the diquark coupling strength in the NJL model Lagrangian. For the\nparameter $a_4=1-2\\alpha_s/\\pi$ a constant value below about \\num{0.4} is\nneeded to explain hybrid stars with ${\\rm M}_{\\rm max} \\gtrsim 2.0~{\\rm\nM}_\\odot$, which would translate to an effective constant $\\alpha_s\\sim 1$. The\nmatching point with a running coupling at the 1-loop $\\beta$ function level is\nfound to lie outside the range of chemical potentials accessible in NS\ninteriors. A dictionary is provided for translating the free parameters of the\nnlNJL model to those of the ABPR model. Both models are shown to be equivalent\nin the nonperturbative domain but the latter one allows to quantify the\ntransition to the asymptotic behaviour in accordance with perturbative QCD. We\nprovide constraints on parameter sets that fulfill the $2~{\\rm M}_\\odot$ mass\nconstraint for hybrid NSs, as well as the low tidal deformability constraint\nfrom GW170817 by a softening of the EOS on the hybrid NS branch with an early\nonset of deconfinement at ${\\rm M}_{\\rm onset}<1.4~{\\rm M}_\\odot$. We find that\nthe effective constant pairing gap should be around 100 MeV but not exceed\nvalues of about 130 MeV because a further increase of the gap would entail a\nsoftening of the EOS and contradict the $2~{\\rm M}_\\odot$ mass constraint.", "category": "nucl-th" }, { "text": "Approximate symmetries in nuclei and the $2\u03bd\u03b2\u03b2$-decay rate: A nonstandard method for calculating the nuclear $2\\nu\\beta\\beta$ - decay\namplitude is proposed. The method is based on the explicit use of those\napproximate symmetries of a nuclear hamiltonian, which correspond to the\noperators of allowed $\\beta$ -- transitions. Within the framework of the\nproposed method the mentioned amplitude is calculated for a wide range of\nnuclei. The model parameters used in calculations are taken from independent\ndata. Calculated \\bb half-lifes are compared with known experimental data.", "category": "nucl-th" }, { "text": "Chiral electric separation effect in the quark-gluon plasma: In this paper we introduce and compute a new transport coefficient for the\nquark-gluon plasma (QGP) at very high temperature. This new coefficient\n$\\sigma_{\\chi e}$, the CESE (Chiral Electric Separation Effect) conductivity,\nquantifies the amount of axial current $\\vec J_A$ that is generated in response\nto an externally applied electric field $e\\vec E$: $\\vec J_A = \\sigma_{\\chi e}\n(e\\vec E)$. Starting with rather general argument in the kinetic theory\nframework, we show how a characteristic structure $\\sigma_{\\chi e}\\propto \\mu\n\\mu_5$ emerges, which also indicates the CESE as an anomalous transport effect\noccurring only in a parity-odd environment with nonzero axial charge density\n$\\mu_5\\neq 0$. Using the Hard-Thermal-Loop framework the CESE conductivity for\nthe QGP is found to be $\\sigma_{\\chi e} = (\\#) T\\frac{{\\rm Tr}_{\\rm\nf}Q_eQ_A}{g^4\\ln(1/g)} \\frac{\\mu\\mu_5}{T^2}$ to the leading-log accuracy with\nthe numerical constant (#) depending on favor content, e.g. (#)$=14.5163$ for\n$u,d$ light flavors.", "category": "nucl-th" }, { "text": "Examination of the calorimetric spectrum to determine the neutrino mass\n in low-energy electron capture decay: The standard kinematic method for determining neutrino mass from the beta\ndecay of tritium or other isotope is to measure the shape of the electron\nspectrum near the endpoint. It has been known for 30 years that a similar\ndistortion of the \"visible energy\" remaining after electron capture is caused\nby neutrino mass. There has been a resurgence of interest in using this method\nwith 163-Ho. Recent theoretical analyses offer reassurance that there are no\nsignificant theoretical uncertainties. We show that the situation is, however,\nmore complicated, and that the spectrum shape is presently not well enough\nunderstood to permit a sensitive determination of the neutrino mass in this\nway. The theoretical analyses consider only single vacancy states in the\ndaughter 163-Dy atom. It is necessary to consider configurations with more than\none vacancy that can be populated owing to the change in nuclear charge. The\nshakeup and shakeoff theory of Carlson and Nestor is used as a basis for\nestimating the population of double-vacancy states. A spectrum of satellites\nassociated with each primary vacancy created by electron capture is presented.\nThe theory of the calorimetric spectrum is more complicated than has been\ndescribed heretofore. There are numerous shakeup and shakeoff satellites\npresent across the spectrum, and some may be very near the endpoint.", "category": "nucl-th" }, { "text": "Dissipation in finite Fermi systems: We present a systematic theory of dissipation in finite Fermi systems like\nnuclei and metallic clusters. This theory is based on the application of\nsemiclassical methods and random matrix theory to linear response of many-body\nsystems. The theory is developed in the approximation wherein the many-body\nsystem can be treated as a single particle in an effective, time-dependent\nmean-field. We find semiclassical expressions for energy dissipation relevant\nin one-body dissipation in heavy nuclei. We also show that this energy\ndissipation, related to damping of collective excitations, is irreversible. The\nirreversibility is proved by our development of a quantum diffusion equation.\nIt may be noted that the quantum diffusion equation is derived from the von\nNeumann equation and makes no assumption about the initial form of the density\noperator. It is shown that, in the semiclassical limit, the quantum diffusion\nequation reduces to the classical Smoluchowski equation. Further, we show that\nthe dissipation is a purely quantal phenomenon as it is related to the\ngeometric phase acquired by a single-particle wavefunction as the system\nevolves in a slow-varying mean-field. It is explicitly shown that the\ndissipation rate is related to the nature of dynamics and the spectrum of the\nclassical Liouvillian operator. Finally, we present an expression for the\nviscosity tensor encountered in nuclear fission in terms of periodic orbits of\nthe single particle in an adiabatically deforming nucleus.", "category": "nucl-th" }, { "text": "Bulk Viscosity of Hot Quark Plasma from Non-Equilibrium Statistical\n Operator: We provide a discussion of the bulk viscosity of two-flavor quark plasma,\ndescribed by the Nambu--Jona-Lasinio model, within the framework of\nKubo-Zubarev formalism. This discussion, which is complementary to our earlier\nstudy, contains a new, detailed derivation of the bulk viscosity in the case of\nmultiple conserved charges. We also provide some numerical details of the\ncomputation of the bulk viscosity close to the Mott transition line, where the\ndissipation is dominated by decays of mesons into quarks and their inverse\nprocesses. We close with a summary of our current understanding of this\nquantity, which stresses the importance of loop resummation for obtaining the\nqualitatively correct result near the Mott line.", "category": "nucl-th" }, { "text": "${}^{7}$Li($d$,$p$)${}^{8}$Li transfer reaction in the NCSM/RGM approach: Recently, we applied an $ab$ $initio$ method, the no-core shell model\ncombined with the resonating group method, to the transfer reactions with light\np-shell nuclei as targets and deuteron as the projectile. In particular, we\nstudied the elastic scattering of deuterium on $^7$Li and the\n${}^{7}$Li($d$,$p$)${}^{8}$Li transfer reaction starting from a realistic\ntwo-nucleon interaction. In this contribution, we review of our main results on\nthe ${}^{7}$Li($d$,$p$)${}^{8}$Li transfer reaction, and we extend the study of\nthe relevant reaction channels, by showing the dominant resonant phase shifts\nof the scattering matrix. We assess also the impact of the polarization effects\nof the deuteron below the breakup on the positive-parity resonant states in the\nreaction. For this purpose, we perform an analysis of the convergence trend of\nthe phase and eigenphase shifts, with respect to the number of deuteron\npseudostates included in the model space.", "category": "nucl-th" }, { "text": "Correlation between the nuclear structure and reaction dynamics of\n Ar-isotopes as projectile using the relativistic mean-field approach: This theoretical study is devoted to bridging the gap between the nuclear\nstructure and reaction dynamics and unravelling their impact on each other,\nconsidering the neutron-rich light mass 30-60Ar isotopes. Using the\nrelativistic mean-field with the NL3* parameter set, several bulk properties\nsuch as binding energies, charge radii, quadrupole deformation parameter, two\nneutron separation energy, and differential two neutron separation energy with\nthe shell closure parameter are probed for the mentioned isotopic chain. For\nvalidation, the RMF (NL3*) results are compared with those obtained from the\nfinite range droplet model (FRDM), Weizsacker-Skyrme model with WS3, WS*\nparameters and the available experimental data. Most of the participating\nisotopes are found to be prolate in structure and neutron shell closures are\nconspicuously revealed at N=14, 20, 40 but weakly shown at N=24, 28, 34. From\nour analysis, a central depletion in the nucleonic density is identified in\n32Ar and 42-58Ar, indicating them as possible candidates for a semi-bubble-like\nstructure. Interestingly, these results are consistent with recent theoretical\nand experimentally measured data. Besides, using the Glauber model, the\nreaction cross-sections are determined by taking 26-48Ar as projectiles and\nstable targets such as 12C, 16O, 40Ca, 90Zr, 124,132Sn, 208Pb and 304120.\nAlthough there is no experimental evidence for the stability of 304120, it has\nbeen predicted in Ref. [Mod. Phys. Lett. A {\\bf 27}, 1250173 (2012)] as a\nstable nucleus. A relatively higher cross-section value is noticed between 30Ar\nand 32Ar which infers that 32Ar is the most stable isotope among the considered\nchain. Moreover, we noticed that the profile of the differential cross-sections\nand scattering angle are highly influenced by the mass of the target nuclei and\nthe magnitude of the incident energy of the projectile nucleus.", "category": "nucl-th" }, { "text": "Spatial orientation of the fission fragment intrinsic spins and their\n correlations: New experimental and theoretical results obtained in 2021 made it acutely\nclear that more than 80 years after the discovery of nuclear fission we do not\nunderstand the generation and dynamics of fission fragment (FF) intrinsic spins\nwell, in particular their magnitudes, their spatial orientation, and their\ncorrelations. The magnitude and orientation of the primary FFs have a crucial\nrole in defining the angular distribution and correlation between the emitted\nprompt neutrons, and subsequent emission of statistical (predominantly E1) and\nstretched E2 {\\gamma}-rays, and their correlations with the final fission\nfragments. Here we present detailed microscopic evaluations of the FF intrinsic\nspins, for both even- and odd-mass FFs, and of their spatial correlations.\nThese point to a well-defined 3D FF intrinsic spin dynamics, characteristics\nabsent in semi-phenomenological studies, due to the presence of the twisting\nspin modes, which artificially were suppressed in semi-phenomenological\nstudies.", "category": "nucl-th" }, { "text": "Phi meson propagation in a hot hadronic gas: The Hidden Local Symmetry Lagrangian is used to study the interactions of phi\nmesons with other pseudoscalar and vector mesons in a hadronic gas at finite\ntemperature. We have found a significantly small phi mean free path (less than\n2.4 fm at T > 170 MeV) due to large collision rates with rho mesons, kaons and\npredominantly K* in spite of their heavy mass. This implies that phi mesons\nproduced after hadronization in relativistic heavy ion collisions will not\nleave the hadronic system without scattering. The effect of these interactions\non the time evolution of the phi density in the expanding hadronic fireball is\ninvestigated.", "category": "nucl-th" }, { "text": "Multiple pion production from an oriented chiral condensate: We consider an ``oriented'' chiral condensate produced in the squeezed states\nof the effective field theory with time- and space-dependent pion mass\nparameter. We discuss the general properties of the solution, identifying\ncondensate modes and determining the resulting pion distributions. The\nimplementation of the dynamics in the form of sudden perturbation allows us to\nlook for exact solutions. In the region of condensation, the dramatic increase\nin pion production and charge fluctuations are demonstrated.", "category": "nucl-th" }, { "text": "Isospin Lattice Gas Model and Nuclear-Matter Phase Diagram and\n Pressure-Volume Isotherms: We study a cubic lattice gas model for nuclear matter where each lattice site\ncan be either occupied, by one proton or one neutron, or unoccupied. A\nnearest-neighbor interaction of the form $ - \\sum_{} J_{ij}\\tau_{zi}\n\\tau_{zj}$ is assumed. Our model is an isospin-1 Ising model, with ${\\tau_z}$ =\n(1,0,-1) representing respectively (proton, vacancy, neutron).\n A kinetic-energy term has been included in our model. Under the\nBragg-Williams mean field approximation our model exhibits the existence of a\ndense phase (liquid-like) and a rare phase (gas-like). The nuclear-matter p-v\nisotherms given by our model are discussed.", "category": "nucl-th" }, { "text": "Properties of strange quark stars with isovector interactions: We study the properties of strange quark stars by employing a 3-flavor\nNambu-Jona-Lasinio model with both scalar-isovector and vector-isovector\ninteractions. Using the constraint on the vector-isoscalar interaction strength\nobtained from the elliptic flow splitting between particles and their\nantiparticles in relativistic heavy-ion collisions, we investigate the\ndependence of the properties of strange quark stars on the vector-isovector and\nthe scalar-isovector interactions, and compare the results with the\nstate-of-art astrophysical constraints on the compact star radius and mass as\nwell as its tidal deformability from the GW170817 event. Results from our study\nreinforce the prospect of using both heavy-ion collisions and astrophysical\nobservations to provide constraints on the isovector coupling strength in quark\nmatter and thus the quark matter equation of state as well as the QCD phase\nstructure at finite isospin chemical potentials.", "category": "nucl-th" }, { "text": "Photoprocesses for the 3H4He and 3He4He channels in the cluster\n potential model: Radiative capture in the 4He3H and 4He3He channels are considered for the 7Li\nand 7Be nuclei. The analysis is based on the corresponding two-cluster models.\nThe potentials of cluster interaction include forbidden states and are made to\nbe consistent with the phase shifts of elastic scattering at energies up to 20\nMeV. Such an approach is shown to describe the total cross sections for\nphotoprocesses over the entire energy region under consideration.", "category": "nucl-th" }, { "text": "A shell model mass formula for exotic light nuclei: An analytic phenomenological shell model mass formula for light nuclei is\nconstructed., The formula takes into account the non locality of the self\nconsistent single particle potential and the special features of light nuclei,\nnamely: a) charge and mass distributions are closer to a Gaussian shape than to\nthe shape characteristic in medium and heavy nuclei; b) the central charge and\nmass densities are larger than, and decrease towards, the \"asymptotic\" values\nthat are the reference parameters for nuclear matter; and c) after a shell\nclosure, the next level has a larger orbital angular momentum and a noticeably\nlarger mean square radius. Only then a good numerical fit is obtained with\nparameters consistent with optical model analysis and empirical spin-orbit\ncouplings. A correlation between the \"skin effect\" and the symmetry dependence\nof the optical potential is established. Towards the neutron drip line the\npotential well depth, the spin-orbit splitting of the single particle levels\nand the gap between major shells decrease, as has been observed. The ensuing\nshift and contraction of the single particle level scheme may lead to: a) to\nstrong configuration mixing and new magic numbers, and b) the onset of the halo\neffect, to avoid the expulsion of single particle levels to the continuum.", "category": "nucl-th" }, { "text": "Prospects of Event Shape Sorting: Event Shape Sorting is a novel method which is devised to organise a sample\nof collision events in such a way, that events with similar final state\ndistribution of hadrons end up sorted close to each other. Such events are\nlikely to have evolved similarly. Thus the method allows to focus at finer\nfeatures of the collision evolution because it would allow for averages over\nsimilar events that do not wash away these features. The algorithm is shortly\nexplained. We also point out the distinction of Event Shape Sorting from the\nwell established technique of Event Shape Engineering.", "category": "nucl-th" }, { "text": "The in-medium few-body problem: We are concerned with few-particle correlations in a fermionic system at\nfinite temperature and density. Within the many-body Green functions formalism\nthe description of correlations is provided by the Dyson equation approach that\nleads to effective few-body equations. They contain the dominant medium\neffects, which are self energy corrections and the Pauli blocking. Hence the\neffective two-body interactions between quasiparticles are\nmomentum/energy-dependent and therefore they can be usesed in the medium\nmodified, momentum space, integral AGS equations for three- and four-body\nsystems. To investigate correlations and clusters beyond four-body, we employ,\ninstead, the configuration space two-variable integro-differential equations\n(IDEA) for $A$-body bound systems which are based on Hyperspherical Harmonics\nand the Faddeev decomposition of the wave function in two-body amplitudes. This\nrequires the transformation of the energy dependent two-body interactions to\nequivalent local, energy independent, ones. To achieve this we use inverse\nscattering techniques the resulting interactions being, on-- and (to all\npractical purposes) off--shell equivalent to the energy dependent potentials.\nIn this way we obtain binding energy results for the 2--, 3--, 4--, and\n16--particle in a medium at a finite temperature and various densities. Several\naspects of the problem are discussed and the behavior of the potential surfaces\nobtained in the extreme adiabatic approximation, below and above the Mott\ntransition, is investigated.", "category": "nucl-th" }, { "text": "Neutral Pion Photoproduction on Nuclei in Baryon Chiral Perturbation\n Theory: Threshold neutral pion photoproduction on light nuclei is studied in the\nframework of baryon chiral perturbation theory. We obtain a general formula for\nthe electric dipole amplitude in the special case of neutral pion\nphotoproduction on a nucleus. To third order in small momenta, the amplitude is\na sum of 2- and 3-body interactions with no undetermined parameters. With\nreasonable input from the single nucleon sector, our result for neutral pion\nphotoproduction on the deuteron is in agreement with experiment.", "category": "nucl-th" }, { "text": "Leading order relativistic chiral nucleon-nucleon interaction: Motivated by the successes of relativistic theories in studies of\natomic/molecular and nuclear systems and the need for a relativistic chiral\nforce in relativistic nuclear structure studies, we explore a new relativistic\nscheme to construct the nucleon-nucleon interaction in the framework of\ncovariant chiral effective field theory. The chiral interaction is formulated\nup to leading order with covariant power counting and a Lorentz invariant\nchiral Lagrangian. We find that the relativistic scheme induces all six spin\noperators needed to describe the nuclear force. A detailed investigation of the\npartial wave potentials shows a better description of the $^1S_0$ and $^3P_0$\nphase shifts than the leading order Weinberg approach, and similar to that of\nthe next-to-leading order Weinberg approach. For the other partial waves with\nangular momenta $J\\geq 1$, the relativistic results are almost the same as\ntheir leading order non-relativistic counterparts.", "category": "nucl-th" }, { "text": "The CSM extension for description of the positive and negative parity\n bands in even-odd nuclei: A particle-core Hamiltonian is used to describe the lowest parity partner\nbands $K^{\\pi}=1/2^{\\pm}$ in\n $^{219}$Ra, $^{237}$U and $^{239}$Pu, and three parity partner bands,\n$K^{\\pi}=1/2^{\\pm}, 3/2^{\\pm}, 5/2^{\\pm}$, in $^{227}$Ra. The core is described\nby a quadrupole and octupole boson Hamiltonian which was previously used for\nthe description of four positive and four negative parity bands in the\nneighboring even-even isotopes. The particle-core Hamiltonian consists of four\nterms: a quadrupole-quadrupole, an octupole-octupole, a spin-spin and a\nrotational $\\hat{I}^2$ interaction, with $\\hat {I}$ denoting the total angular\nmomentum. The single particle space for the odd nucleon consists of three\nspherical shell model states, two of positive and one of negative parity. The\nproduct of these states with a collective deformed ground state and the\nintrinsic gamma band state generate, through angular momentum projection, the\nbands with $K^{\\pi}=1/2^{\\pm},3/2^{\\pm},5/2^{\\pm}$, respectively. In the space\nof projected states one calculates the energies of the considered bands. The\nresulting excitation energies are compared with the corresponding experimental\ndata as well as with those obtained with other approaches. Also, we searched\nfor some signatures for a static octupole deformation in the considered odd\nisotopes. The calculated branching ratios in $^{219}$Ra agree quite well with\nthe corresponding experimental data.", "category": "nucl-th" }, { "text": "Electroweak Hard Photon Bremsstrahlung in Electron-Nucleon Scattering: One way to treat the infrared divergences of the electroweak\nNext-to-Leading-Order (NLO) differential cross sections to parity-violating\n(PV) electron-proton scattering is by adding soft-photon emission contribution.\nAlthough more physical, the results are left with a logarithmic dependence on\nthe photon detector acceptance, which can only be eliminated by considering\nHard Photon Bremsstrahlung (HPB) contribution. Here we present a treatment of\nHPB for PV electron-proton scattering. HPB differential cross sections for\nelectron-proton scattering have been computed using the experimental values of\nnucleon form factors. The final results are expressed through kinematic\nparameters, making it possible to apply the computed PV HPB differential cross\nsections for the analysis of data of a range of current and proposed\nexperiments.", "category": "nucl-th" }, { "text": "Equation of state in the inner crust of neutron stars: discusion of the\n unbound neutron states: In this paper, we calculate the stable Wigner-Seitz (W-S) cells in the inner\ncrust of neutron stars and we discuss the nuclear shell effects. A distinction\nis done between the shell effects due to the bound states and those induced by\nthe unbound states, which are shown to be spurious. We then estimate the\neffects of the spurious shells on the total energy and decompose it into a\nsmooth and a residual part. We propose a correction to the Hartree-Fock binding\nenergy in Wigner-Seitz cell (HF-WS).", "category": "nucl-th" }, { "text": "Phase diagram of dilute cosmic matter: Enhancement of nuclear pasta formation due to multi-nucleus simultaneous\ncollision is presented based on time-dependent density functional calculations\nwith periodic boundary condition. This calculation corresponds to the situation\nwith density lower than the known low-density existence limit of the nuclear\npasta phase. In order to evaluate the contribution from three-nucleus\nsimultaneous collisions inside the cosmic matter, the possibility of\nmulti-nucleus simultaneous collisions is examined by a systematic Monte-Carlo\ncalculation, and the mean free path of a nucleus is obtained. Consequently the\nlow-density existence limit of the nuclear pasta phase is formed to be lower\nthan believed up to now.", "category": "nucl-th" }, { "text": "Extracting the QGP viscosity from RHIC data -- a status report from\n viscous hydrodynamics: We report recent progress on causal viscous hydrodynamics for relativistic\nheavy ion collisions. For fixed specific shear viscosity eta/s, uncertainties\nin the elliptic flow arising from initial conditions, equation of state, bulk\nviscosity and numerical viscosity, and the treatment of the highly viscous\nhadronic stage and freeze-out procedure are analysed. A comparison of current\nviscous hydrodynamic results with experimental data yields a robust upper limit\neta/s < 5/(4pi).", "category": "nucl-th" }, { "text": "Dilepton production in elementary and in heavy ion reactions: We present a unified description of the vector meson and dilepton production\nin elementary and in heavy ion reactions. The production of vector mesons\n($\\rho,\\omega,\\phi$) is described via the excitation of nucleon resonances\n($R$). The theoretical framework is an extended vector meson dominance model\n(eVMD) for resonance decays $R\\longmapsto NV$ with arbitrary spin which is\ncovariant and kinematically complete. The eVMD includes thereby excited vector\nmeson states in the transition form factors. The model has successfully been\napplied to $\\omega$ and $\\phi$ production in $p+p$ reactions. The same model is\nused to describe the dilepton production in elementary reactions where\ncorresponding data are well reproduced. However, when the model is applied to\nheavy ion reactions in the BEVALAC/SIS energy range the experimental dilepton\nspectra measured by the DLS Collaboration are significantly underestimated at\nsmall invariant masses. In view of this fact we discuss further medium effects:\nOne is a substantial collisional broadening of the $\\rho$ and in particular of\nthe $\\omega$ meson in the vicinity of the $\\rho/\\omega$-peak. The second medium\neffect is the destruction of quantum interference in a dense medium. A\ndecoherent dilepton emission through vector mesons decays enhances the\ncorresponding low mass dilepton yield in heavy ion reactions and improves the\nagreement with existing data.", "category": "nucl-th" }, { "text": "Numerical Simulation of the Hydrodynamical Combustion to Strange Quark\n Matter: We present results from a numerical solution to the burning of neutron matter\ninside a cold neutron star into stable (u,d,s) quark matter. Our method solves\nhydrodynamical flow equations in 1D with neutrino emission from weak\nequilibrating reactions, and strange quark diffusion across the burning front.\nWe also include entropy change due to heat released in forming the stable quark\nphase. Our numerical results suggest burning front laminar speeds of 0.002-0.04\ntimes the speed of light, much faster than previous estimates derived using\nonly a reactive-diffusive description. Analytic solutions to hydrodynamical\njump conditions with a temperature dependent equation of state agree very well\nwith our numerical findings for fluid velocities. The most important effect of\nneutrino cooling is that the conversion front stalls at lower density (below\napproximately 2 times saturation density). In a 2-dimensional setting, such\nrapid speeds and neutrino cooling may allow for a flame wrinkle instability to\ndevelop, possibly leading to detonation.", "category": "nucl-th" }, { "text": "Parity-Violating Interaction Effects in the np System: We investigate parity-violating observables in the np system, including the\nlongitudinal asymmetry and neutron-spin rotation in np elastic scattering, the\nphoton asymmetry in np radiative capture, and the asymmetries in deuteron\nphoto-disintegration d(gamma,n)p in the threshold region and\nelectro-disintegration d(e,e`)np in quasi-elastic kinematics. To have an\nestimate of the model dependence for the various predictions, a number of\ndifferent, latest-generation strong-interaction potentials--Argonne v18, Bonn\n2000, and Nijmegen I--are used in combination with a weak-interaction potential\nconsisting of pi-, rho-, and omega-meson exchanges--the model known as DDH. The\ncomplete bound and scattering problems in the presence of parity-conserving,\nincluding electromagnetic, and parity-violating potentials is solved in both\nconfiguration and momentum space. The issue of electromagnetic current\nconservation is examined carefully. We find large cancellations between the\nasymmetries induced by the parity-violating interactions and those arising from\nthe associated pion-exchange currents. In the np capture, the model dependence\nis nevertheless quite small, because of constraints arising through the Siegert\nevaluation of the relevant E1 matrix elements. In quasi-elastic electron\nscattering these processes are found to be insignificant compared to the\nasymmetry produced by gamma-Z interference on individual nucleons.", "category": "nucl-th" }, { "text": "Relativistic predictions of polarization phenomena in exclusive\n proton-induced proton-knockout reactions: Whereas a nonrelativistic distorted wave model fails to quantitatively\ndescribe analyzing power data for exclusive proton-induced proton-knockout from\nthe 3s_{1/2} state in Pb-208 at 202 MeV, the corresponding relativistic\nprediction provides a perfect description, thus suggesting that the Dirac\nequation is the more appropriate underlying dynamical equation. We check the\nconsistency of this rsult by comparing predictions for both dynamical models to\nnew high resolution data for 3s_{1/2} knockout in Pb-208 at a higher incident\nenergy of 392 MeV.", "category": "nucl-th" }, { "text": "Initial State Energy Loss Dependence of J/Psi and Drell-Yan in\n Relativistic Heavy Ion Collisions: We present a Glauber-based study of J/Psi and Drell-Yan yields in\nnucleus-nucleus collisions. Using this approach, we have investigated the\nimpact of energy loss by the colliding nuclei on observed yields and transverse\nmomentum spectra of J/Psi and Drell-Yan. These studies permit an assessment of\nthe importance of initial state energy loss in relation to \"anomalous\" J/Psi\nsuppression.", "category": "nucl-th" }, { "text": "Photon bremsstrahlung and diffusive broadening of a hard jet: The photon bremsstrahlung rate from a quark jet produced in deep-inelastic\nscattering (DIS) off a large nucleus is studied in the collinear limit. The\nleading medium-enhanced higher twist corrections which describe the multiple\nscattering of the jet in the nucleus are re-summed to all orders of twist. The\npropagation of the jet in the absence of further radiative energy loss is shown\nto be governed by a transverse momentum diffusion equation. We compute the\nfinal photon spectrum in the limit of soft photons, taking into account the\nleading and next-to-leading terms in the photon momentum fraction y. In this\nlimit, the photon spectrum in a physical gauge is shown to arise from two\ninterfering sources: one where the initial hard scattering produces an\noff-shell quark which immediately radiates the photon and then undergoes\nsubsequent soft re-scattering; alternatively the quark is produced on-shell and\npropagates through the medium until it is driven off-shell by re-scattering and\nradiates the photon. Our result has a simple formal structure as a product of\nthe photon splitting function, the quark transverse momentum distribution\ncoming from a diffusion equation and a dimensionless factor which encodes the\neffect of the interferences encountered by the propagating quark over the\nlength of the medium. The destructive nature of such interferences in the small\ny limit are responsible for the origin of the Landau-Pomeranchuck-Migdal (LPM)\neffect. Along the way we also discuss possible implications for quark jets in\nhot nuclear matter.", "category": "nucl-th" }, { "text": "Equilibrium and non-equilibrium effects in relativistic heavy ion\n collisions: The hypothesis of local equilibrium (LE) in relativistic heavy ion collisions\nat energies from AGS to RHIC is checked in the microscopic transport model. We\nfind that kinetic, thermal, and chemical equilibration of the expanding\nhadronic matter is nearly reached in central collisions at AGS energy for $t\n\\geq 10$ fm/$c$ in a central cell. At these times the equation of state may be\napproximated by a simple dependence $P \\cong (0.12-0.15) \\epsilon$. Increasing\ndeviations of the yields and the energy spectra of hadrons from statistical\nmodel values are observed for increasing bombarding energies. The origin of\nthese deviations is traced to the irreversible multiparticle decays of strings\nand many-body $(N \\geq 3)$ decays of resonances. The violations of LE indicate\nthat the matter in the cell reaches a steady state instead of idealized\nequilibrium. The entropy density in the cell is only about 6% smaller than that\nof the equilibrium state.", "category": "nucl-th" }, { "text": "Nucleon-Nucleon Effective Field Theory Without Pions: Nuclear processes involving momenta much below the mass of the pion may be\ndescribed by an effective field theory in which the pions do not appear as\nexplicit degrees of freedom. The effects of the pion and all other virtual\nhadrons are reproduced by the coefficients of gauge-invariant local operators\ninvolving the nucleon field. Nucleon-nucleon scattering phase shift data\nconstrains many of the coefficients that appear in the effective Lagrangean but\nat some order in the expansion coefficients enter that must be constrained by\nother observables. We compute several observables in the two-nucleon sector up\nto next-to-next-to leading order in the effective field theory without pions,\nor to the order at which a counterterm involving four-nucleon field operators\nis encountered. Effective range theory is recovered from the effective field\ntheory up to the order where relativistic corrections enter or where\nfour-nucleon-external current local operators arise. For the deuteron magnetic\nmoment, quadrupole moment and the $np\\to d\\gamma$ radiative capture cross\nsection a four-nucleon-one-photon counterterm exists at next-to-leading order.\nThe electric polarizability and electric charge form factor of the deuteron are\ndetermined up to next-to-next-to-leading order, which includes the first\nappearance of relativistic corrections.", "category": "nucl-th" }, { "text": "Phase Transition Study meets Machine Learning: In recent years, machine learning (ML) techniques have emerged as powerful\ntools for studying many-body complex systems, and encompassing phase\ntransitions in various domains of physics. This mini review provides a concise\nyet comprehensive examination of the advancements achieved in applying ML to\ninvestigate phase transitions, with a primary focus on those involved in\nnuclear matter studies.", "category": "nucl-th" }, { "text": "Coulomb screening correction to the $Q$ value of the triple alpha\n process in thermal plasmas: The triple alpha reaction is a key to $^{12}$C production and is expected to\noccur in weakly-coupled, thermal plasmas as encountered in normal stars. We\ninvestigate how Coulomb screening affects the structure of a system of three\nalpha particles in such a plasma environment by precise three-body calculations\nwithin the Debye-H\\\"uckel approximation. A three-alpha model that has the\nCoulomb interaction modified in the Yukawa form is employed. Precise three-body\nwave functions are obtained by a superposition of correlated Gaussian bases\nwith the aid of the stochastic variational method. The energy shifts of the\nHoyle state due to the Coulomb screening are obtained as a function of the\nDebye screening length. The results, which automatically incorporate the finite\nsize effect of the Hoyle state, are consistent with the conventional result\nbased on the Coulomb correction to the chemical potentials of ions that are\nregarded as point charges in a weakly-coupled, thermal plasma. We have given a\ntheoretical basis to the conventional point-charge approach to the Coulomb\nscreening problem relevant for nuclear reactions in normal stars by providing\nthe first evaluation of the Coulomb corrections to the $Q$ value of the triple\nalpha process that produces a finite size Hoyle state.", "category": "nucl-th" }, { "text": "Measuring charge fluctuations in high-energy nuclear collisions: Various measures of charge fluctuations in heavy-ion collisions are\ndiscussed. Advantages of the Phi-measure are demonstrated and its relation to\nother fluctuation measures is established. To get the relation, Phi is\nexpressed through the moments of multiplicity distribution. We study how the\nmeasures act in the case of a `background' model which represents the classical\nhadron gas in equilibrium. The model assumes statistical particle production\nconstrained by charge conservation. It also takes into account both the effect\nof incomplete experimental apparatus acceptance and that of tracking\ninefficiency. The model is shown to approximately agree with the PHENIX and\npreliminary STAR data on the electric charge fluctuations. Finally,\n`background-free' measures are discussed.", "category": "nucl-th" }, { "text": "Hyperons, deconfinement and the speed of sound in neutron stars: The effects of the presence of hyperons and a phase transition to deconfined\nquark matter on the speed of sound in neutron stars is investigated. For this\npurpose a composite description consisting of a model of the covariant field\ntheory of hadrons and one for unbound quarks are used. A phase transition with\ncontinuous and monotonous variation of the equation of state is assumed. The\npredictions are contrasted with recent observational data on isolated neutron\nstars as well as on binary systems. Only one candidate is finally obtained from\nsix different descriptions. According to the present calculations the onset of\nthe hyperons causes the equilibrium speed of sound to exceed the conformal\nlimit. Qualitative agreement with recent work about the influence of the speed\nof sound on the g-modes of oscillation in neutron stars is obtained.", "category": "nucl-th" }, { "text": "Supernarrow Dibaryons and Exotic Baryons with Small Masses: A searche for supernarrow dibaryons (SND) and exotic baryons with small\nmasses is reviewed. As a result of the study of the reaction pd->p+pX_1, three\nnarrow peaks at M_{pX_1}=1904, 1926, and 1942 MeV have been observed. The\nanalysis of the angular distributions of the protons from the decay of the pX_1\nstates showed that the peaks found can be explained as a manifestation of the\nisovector SNDs, the decay of which into two nucleons is forbidden by the Pauli\nexclusion principle. The observation of the peaks in the missing mass M_{X_1}\nspectra at 966, 986, and 1003 MeV is an additional indication that the\ndibaryons found are the SNDs. The possible interpretation of these peaks in the\nM_{X_1} mass spectra and peaks observed in the reaction pp->pi^+pX at M_X=1004,\n1044, and 1094 MeV as new exotic baryon states with small masses is discussed.\nThe mass equation has been constructed which is used to calculate the masses\nand determine parities of the exotic baryons. The obtained values of the masses\nare in a good agreement with the experimental data. Two new exotic baryon\nstates bellow the \\pi production threshold have been predicted.", "category": "nucl-th" }, { "text": "Faddeev approach to confined three-quark problems: We propose a method that allows for the efficient solution of the three-body\nFaddeev equations in the presence of infinitely rising confinement\ninteractions. Such a method is useful in calculations of nonrelativistic and\nespecially semirelativistic constituent quark models. The convergence of the\npartial wave series is accelerated and possible spurious contributions in the\nFaddeev components are avoided. We demonstrate how the method works with the\nexample of the Goldstone-boson-exchange chiral quark model for baryons.", "category": "nucl-th" }, { "text": "Direct Reactions with Exotic Nuclei: We discuss recent work on Coulomb dissociation and an effective-range theory\nof low-lying electromagnetic strength of halo nuclei. We propose to study\nCoulomb dissociation of a halo nucleus bound by a zero-range potential as a\nhomework problem. We study the transition from stripping to bound and unbound\nstates and point out in this context that the Trojan-Horse method is a suitable\ntool to investigate subthreshold resonances.", "category": "nucl-th" }, { "text": "Study of nuclear dynamics of neutron-rich colliding pair at energy of\n vanishing flow: We study nuclear dynamics at the energy of vanishing flow of neutron-rich\nsystems having N/Z ratio 1.0, 1.6 and 2.0 throughout the mass range at semi\ncentral colliding geometry. In particular we study the behavior of average and\nmaximum density with N/Z dependence of the system.", "category": "nucl-th" }, { "text": "Flow harmonics from self-consistent particlization of a viscous fluid: The quantitative extraction of quark-gluon plasma (QGP) properties from\nheavy-ion data, such as its specific shear viscosity $\\eta /s$, typically\nrequires comparison to viscous hydrodynamic or \"hybrid\" hydrodynamics+transport\nsimulations. In either case, one has to convert the fluid to hadrons, yet\nwithout additional theory input the conversion is ambiguous for dissipative\nfluids. Here, shear viscous phase-space corrections calculated using linearized\ntransport theory are applied in Cooper-Frye freezeout to quantify the effects\non anisotropic flow coefficients $v_n(p_T)$ at both RHIC and LHC energies.\nExpanding upon our previous flow harmonics studies [1,2], we calculate pion and\nproton $v_2(p_T)$, $v_4(p_T)$, and $v_6(p_T)$. Unlike in Ref. [1], we\nincorporate a hadron gas that is chemically frozen below a temperature of 175\nMeV, and use hypersurfaces from realistic viscous hydrodynamic simulations.\nWith additive quark model cross sections and relative phase-space corrections\nwith $p^{3/2}$ momentum dependence, rather than the quadratic Grad form, we\nfind at moderately high transverse momentum noticeably higher $v_4(p_T)$ and\n$v_6(p_T)$ for protons than for pions. In addition, the value of $\\eta /s$\ndeduced from elliptic flow data differs by nearly 50\\% from the value extracted\nusing the naive \"democratic Grad\" form of freeze-out distributions. To\nfacilitate the use of the self-consistent viscous corrections calculated here\nin hydrodynamic and hybrid calculations, we also present convenient\nparameterizations of the corrections for the various hadron species (cf. Table\nI).", "category": "nucl-th" }, { "text": "Analysis of previous microscopic calculations for second $0^+$ state in\n $^{12}$C in terms of 3-alpha particle Bose-condensed state: The wave function of the second $0^+$ state of $^{12}$C which was obtained\nlong time ago by solving the microscopic 3$\\alpha$ problem is shown to be\nalmost completely equivalent to the wave function of the 3$\\alpha$ condensed\nstate which has been proposed recently by the present authors. This equivalence\nof the wave functions is shown to hold in two cases where different effective\ntwo-nucleon forces are adopted. This finding gives strong support for\ninterpreting the second $0^+$ state of $^{12}$C which is the key state for the\nsynthesis of $^{12}$C in stars ('Hoyle' state), and which is one of the typical\nmysterious $0^+$ states in light nuclei, as a gas-like structure of three\n$\\alpha$ particles, Bose-condensed into an identical s-wave function.", "category": "nucl-th" }, { "text": "Density functional approaches to collective phenomena in nuclei:\n Time-dependent density-functional theory for perturbative and\n non-perturbative nuclear dynamics: We present the basic concepts and our recent developments in the density\nfunctional approaches with the Skyrme functionals for describing nuclear\ndynamics at low energy. The time-dependent density-functional theory (TDDFT) is\nutilized for the exact linear response with an external perturbation. For\ndescription of collective dynamics beyond the perturbative regime, we present a\ntheory of a decoupled collective submanifold to describe for a slow motion\nbased on the TDDFT. Selected applications are shown to demonstrate the quality\nof their performance and feasibility. Advantages and disadvantages in the\nnumerical aspects are also discussed.", "category": "nucl-th" }, { "text": "Non-empirical shape dynamics of heavy nuclei with multi-task deep\n learning: A microscopic description of nuclear fission represents one of the most\nchallenging problems in nuclear theory. While phenomenological coordinates,\nsuch as multipole moments, have often been employed to describe fission, it is\nnot obvious whether these parameters fully reflect the shape dynamics of\ninterest. We here propose a novel method to extract collective coordinates,\nwhich are free from phenomenology, based on multi-task deep learning in\nconjunction with a density functional theory (DFT). To this end, we first\nintroduce randomly generated external fields to a Skyrme-EDF and construct a\nset of nuclear number densities and binding energies for deformed states of\n${}^{236}$U around the ground state. By training a neural network on such\ndataset with a combination of an autoencoder and supervised learning, we\nsuccessfully identify a two-dimensional latent variables that accurately\nreproduce both the energies and the densities of the original Skyrme-EDF\ncalculations, within a mean absolute error of 113 keV for the energies. In\ncontrast, when multipole moments are used as latent variables for training in\nconstructing the decoders, we find that the training data for the binding\nenergies are reproduced only within 2 MeV. This implies that conventional\nmultipole moments do not provide fully adequate variables for a shape dynamics\nof heavy nuclei.", "category": "nucl-th" }, { "text": "A study of the phase transition in the usual statistical model for\n nuclear multifragmentation: We use a simplified model which is based on the same physics as inherent in\nmost statistical models for nuclear multifragmentation. The simplified model\nallows exact calculations for thermodynamic properties of systems of large\nnumber of particles. This enables us to study a phase transition in the model.\nA first order phase transition can be tracked down. There are significant\ndifferences between this phase transition and some other well-known cases.", "category": "nucl-th" }, { "text": "Particle Interferometry for Relativistic Heavy-Ion Collisions: In this report we give a detailed account on Hanbury Brown/Twiss (HBT)\nparticle interferometric methods for relativistic heavy-ion collisions. These\nexploit identical two-particle correlations to gain access to the space-time\ngeometry and dynamics of the final freeze-out stage. The connection between the\nmeasured correlations in momentum space and the phase-space structure of the\nparticle emitter is established, both with and without final state\ninteractions. Suitable Gaussian parametrizations for the two-particle\ncorrelation function are derived and the physical interpretation of their\nparameters is explained. After reviewing various model studies, we show how a\ncombined analysis of single- and two-particle spectra allows to reconstruct the\nfinal state of relativistic heavy-ion collisions.", "category": "nucl-th" }, { "text": "Does \u03a3-\u03a3-\u03b1Form a Quasi-Bound State?: We have investigated the possible existence of a quasi-bound state for the\n\\Sigma -\\Sigma -\\alpha system in the framework of Faddeev calculations. We are\nparticularly interested in the state of total iso-spin T=2, since for an inert\n\\alpha particle there is no strong conversion to \\Xi -N-\\alpha or \\Lambda\n-\\Lambda -\\alpha possible. A \\Sigma -\\alpha optical potential based on Nijmegen\nmodel D and original \\Sigma -\\Sigma interactions of the series of Nijmegen\npotentials NSC97 as well a simulated Gaussian type versions thereof are used.\nOur investigation of the \\Sigma -\\Sigma -\\alpha system leads to a quasi bound\nstate where, depending on the potential parameters, the energy ranges between\n-1.4 and -2.4 MeV and the level width is about 0.2MeV.", "category": "nucl-th" }, { "text": "Repulsive force by vector mesons and quark-hadron phase transition: Using a phenomenological model with vector-type interactions, we discuss a\nrole of repulsive force in the quark-hadron phase transition at high density.\nFor realization of the quark phase at high density, strong vector coupling is\nneeded in the hadron phase, while it is forbidden in the quark phase. For the\nquark-phase, a NJL-type model with a multi-quark interaction is investigated.\nWe show that, in this model, the restoration of chiral symmetry decreases\neffective vector coupling and the quark phase is realized at high density, even\nif we have strong vector coupling at low density. In this model, the strong\ncoupling in the hadron phase is induced by the chiral symmetry breaking.", "category": "nucl-th" }, { "text": "Realistic medium-averaging in radiative energy loss: We present results from a jet energy loss calculation using the\nGyulassy-Levai-Vitev (GLV) formalism and bulk medium evolution from the\ncovariant transport model MPC. At both RHIC and LHC energies we find that\nrealistic transverse expansion strongly reduces elliptic flow at high pT\ncompared to calculations with transversely 'frozen' profiles. We argue that\nthis is a generic feature of GLV energy loss. Transverse expansion also leads\nto stronger high-pT suppression, while fluctuations in energy loss with the\nlocation of scattering centers weaken the suppression. But, unlike the\nreduction of v2, these effects nearly disappear once alpha_s is adjusted to\nreproduce R_AA in central collisions.", "category": "nucl-th" }, { "text": "Tensor correlations in $^4$He and $^8$Be with antisymmetrized quasi\n cluster model: In this paper, we extend the framework of improved version of simplified\nmethod to take into account the tensor contribution ($i$SMT) and propose\nAQCM-T, tensor version of antisymmetrized quasi cluster model (AQCM). Although\nAQCM-T is phenomenological, we can treat the $^3S$-$^3D$ coupling in the\ndeuteron-like $T=0$ $NN$-pair induced by the tensor interaction in a very\nsimplified way, which allows us to proceed to heavier nuclei. Also we propose a\nnew effective interaction, V2m, where the triplet-even channel of the Volkov\nNo.2 interaction is weakened to 60% so as to reproduce the binding energy of\n$^4$He after including the tensor term of a realistic interaction. Using AQCM-T\nand the new interaction, the significant tensor contribution in $^4$He is\nshown, which is almost comparable the central interaction, where $D$-state\nmixes by 8% to the major $S$-state. The AQCM-T model with the new interaction\nis also applied to $^8$Be. It is found that the tensor suppression gives\nsignificant contribution to the short-range repulsion between two {\\alpha}\nclusters.", "category": "nucl-th" }, { "text": "Fluctuations of rare particles as a measure of chemical equilibration: We calculate the time evolution of fluctuations for rare particles such as\ne.g. kaons in 1 AGeV or charmonium in 200 AGeV heavy ion collisions. We find\nthat these fluctuations are a very sensitive probe of the degree of chemical\nequilibration reached in these collisions. Furthermore, measuring the second\nfactorial moment the size of the initial population can be determined.", "category": "nucl-th" }, { "text": "Excited Baryons and Chiral Symmetry Breaking of QCD: N* masses in the spin-1/2 and spin-3/2 sectors are computed using two\nnon-perturbative methods: lattice QCD and QCD sum rules. States with both\npositive and negative parity are isolated via parity projection methods. The\nbasic pattern of the mass splittings is consistent with experiments. The mass\nsplitting within the same parity pair is directly linked to the chiral symmetry\nbreaking QCD.", "category": "nucl-th" }, { "text": "Two-body dissipation effects on synthesis of superheavy elements: To investigate the two-body dissipation effects on the synthesis of\nsuperheavy elements, we calculate low-energy collisions of the $N=50$ isotones\n($^{82}$Ge, $^{84}$Se, $^{86}$Kr and $^{88}$Sr) on $^{208}$Pb using the\ntime-dependent density-matrix theory (TDDM). TDDM is an extension of the\ntime-dependent Hartree-Fock (TDHF) theory and can determine the time evolution\nof one-body and two-body density matrices. Thus TDDM describes both one-body\nand two-body dissipation of collective energies. It is shown that the two-body\ndissipation may increase fusion cross sections and enhance the synthesis of\nsuperheavy elements.", "category": "nucl-th" }, { "text": "Radiative 3He(2H,g)5Li capture at low deuterium energy: The results are presented on the total cross sections, astrophysical\nS-factor, reaction rate of the deuteron radiative capture on 3He at the\ntemperatures from 0.03 up to 3 T9 calculated in the framework of the potential\ncluster model with the forbidden states coming from the classification of the\norbital states by the Young diagrams. Within the used model and exploited Young\ndiagram classification made it possible to reproduce the general features of\nthe available experimental data on the cross section and reconstructed\nastrophysical S-factor in the energy range from 200 keV up to 1.4 MeV. The\nparametrization of the obtained reaction rate has been found and been compared\nwith some other actual reactions with light clusters.", "category": "nucl-th" }, { "text": "Ab Initio Description of p-Shell Hypernuclei: We present the first ab initio calculations for p-shell single-Lambda\nhypernuclei. For the solution of the many-baryon problem, we develop two\nvariants of the no-core shell model with explicit $\\Lambda$ and $\\Sigma^+$,\n$\\Sigma^0$, $\\Sigma^-$ hyperons including $\\Lambda$-$\\Sigma$ conversion,\noptionally supplemented by a similarity renormalization group transformation to\naccelerate model-space convergence. In addition to state-of-the-art chiral two-\nand three-nucleon interactions, we use leading-order chiral hyperon-nucleon\ninteractions and a recent meson-exchange hyperon-nucleon interaction. We\nvalidate the approach for s-shell hypernuclei and apply it to p-shell\nhypernuclei, in particular to $^7_\\Lambda$Li, $^9_\\Lambda$Be and\n$^{13}_\\Lambda$C. We show that the chiral hyperon-nucleon interactions provide\nground-state and excitation energies that agree with experiment within the\ncutoff dependence. At the same time we demonstrate that hypernuclear\nspectroscopy provides tight constraints on the hyperon-nucleon interactions and\nwe discuss the impact of induced hyperon-nucleon-nucleon interactions.", "category": "nucl-th" }, { "text": "Propagation of uncertainties in the nuclear DFT models: Parameters of the nuclear density functional theory (DFT) models are usually\nadjusted to experimental data. As a result they carry certain theoretical\nerror, which, as a consequence, carries out to the predicted quantities. In\nthis work we address the propagation of theoretical error, within the nuclear\nDFT models, from the model parameters to the predicted observables. In\nparticularly, the focus is set on the Skyrme energy density functional models.", "category": "nucl-th" }, { "text": "Quantification of Uncertainties in Nuclear Density Functional theory: Reliable predictions of nuclear properties are needed as much to answer\nfundamental science questions as in applications such as reactor physics or\ndata evaluation. Nuclear density functional theory is currently the only\nmicroscopic, global approach to nuclear structure that is applicable throughout\nthe nuclear chart. In the past few years, a lot of effort has been devoted to\nsetting up a general methodology to assess theoretical uncertainties in nuclear\nDFT calculations. In this paper, we summarize some of the recent progress in\nthis direction. Most of the new material discussed here will be be published in\nseparate articles.", "category": "nucl-th" }, { "text": "Residual cut-off dependence and power counting: the deuteron as a case\n study: Effective field theories (EFTs) require regularization and renormalization to\ngain predictive power. While regularization is inconsequential from the point\nof view of the observable predictions of EFT -- in a renormalized theory we\nexpect predictions to be regulator-independent once the cutoff is removed --\nthe particular details of regulator dependence might provide interesting\ninsights into the inner workings of an EFT. In fact, the analysis of regulator\ndependence has been frequently suggested as a tool to study the ordering scheme\nor power counting of EFTs. We show here that the choice of the regulator might\nimpact the power law properties of the residual cutoff dependence. If this\nconclusion were to be confirmed, it would have consequences on the validity of\nthis method as a tool to analyze power counting.", "category": "nucl-th" }, { "text": "Symmetry background of the stability of the second 0^+ state of 4^He: It was found in this paper that the dominant component of the wave function\nof the second 0^+ state of 4^He and the corresponding component of the 3^H+p\nchannel have different spatial permutation symmetries. This fact will hinder\nthe wave function to extend from the interior region to the outgoing channel\nand will lead to a narrower width.", "category": "nucl-th" }, { "text": "Chemical freezeout parameters within generic nonextensive statistics: The particle production in relativistic heavy-ion collisions seems to be\ncreated in a dynamically disordered system which can be best described by an\nextended exponential entropy. In distinguishing between the applicability of\nthis and Boltzmann-Gibbs (BG) in generating various particle-ratios, generic\n(non)extensive statistics (GNS) is introduced to the hadron resonance gas\nmodel. Accordingly, the degree of (non)extensivity is determined by the\npossible modifications in the phase space. Both BG extensivity and Tsallis\nnonextensivity are included as very special cases defined by specific values of\nthe equivalence classes $(c, d)$. We found that the particle ratios at energies\nranging between $3.8$ and $2760~$GeV are best reproduced by nonextensive\nstatistics, where $c$ and $d$ range between $\\sim0.9$ and $\\sim1$. The present\nwork aims at illustrating that the proposed approach is well capable to\nmanifest the statistical nature of the system on interest. We don't aim at\nhighlighting deeper physical insights. In other words, while the resulting\nnonextensivity is neither BG nor Tsallis, the freezeout parameters are found\nvery compatible with BG and accordingly with the well-known freezeout\nphase-diagram, which is in an excellent agreement with recent lattice\ncalculations. We conclude that the particle production is nonextensive but\nshould not necessarily be accompanied by a radical change in the intensive or\nextensive thermodynamic quantities, such as internal energy and temperature.\nOnly, the two critical exponents defining the equivalence classes $(c, d)$ are\nthe physical parameters characterizing the (non)extensivity.", "category": "nucl-th" }, { "text": "Production of heavy and superheavy nuclei in massive fusion reactions: Within the framework of a dinuclear system (DNS) model, the\nevaporation-residue excitation functions and the quasi-fission mass yields in\nthe $^{48}$Ca induced fusion reactions are investigated systematically and\ncompared with available experimental data. Maximal production cross sections of\nsuperheavy nuclei based on stable actinide targets are obtained. Isotopic\ntrends in the production of the superheavy elements Z=110, 112-118 based on the\nactinide isotopic targets are analyzed systematically. Optimal evaporation\nchannels and combinations as well as the corresponding excitation energies are\nproposed. The possible factors that influencing the isotopic dependence of the\nproduction cross sections are analyzed. The formation of the superheavy nuclei\nbased on the isotopes U with different projectiles are also investigated and\ncalculated.", "category": "nucl-th" }, { "text": "Role of three-nucleon forces and many-body processes in nuclear pairing: We present microscopic valence-shell calculations of pairing gaps in the\ncalcium isotopes, focusing on the role of three-nucleon (3N) forces and\nmany-body processes. In most cases, we find a reduction in pairing strength\nwhen the leading chiral 3N forces are included, compared to results with\nlow-momentum two-nucleon (NN) interactions only. This is in agreement with a\nrecent energy density functional study. At the NN level, calculations that\ninclude particle-particle and hole-hole ladder contributions lead to smaller\npairing gaps compared with experiment. When particle-hole contributions as well\nas the normal-ordered one- and two-body parts of 3N forces are consistently\nincluded to third order, we find reasonable agreement with experimental\nthree-point mass differences. This highlights the important role of 3N forces\nand many-body processes for pairing in nuclei. Finally, we relate pairing gaps\nto the evolution of nuclear structure in neutron-rich calcium isotopes and\nstudy the predictions for the 2+ excitation energies, in particular for 54Ca.", "category": "nucl-th" }, { "text": "Parity-violating nucleon-nucleon interaction from different approaches: Two-pion exchange parity-violating nucleon-nucleon interactions from recent\neffective field theories and earlier fully covariant approaches are\ninvestigated. The potentials are compared with the idea to obtain better\ninsight on the role of low-energy constants appearing in the effective field\ntheory approach and the convergence of this one in terms of a perturbative\nseries. The results are illustrated by considering the longitudinal asymmetry\nof polarized protons scattering off protons, $\\vec{p}+p -> p+p$, and the\nasymmetry of the photon emission in radiative capture of polarized neutrons by\nprotons, $\\vec{n}+p -> d+\\gamma$.", "category": "nucl-th" }, { "text": "Energy Systematics of Jet Tomography at RHIC: sqrt{s} = 62.4 vs 200 AGeV: The collision energy dependence of jet tomography is investigated within the\nGLV formalism. The emphasis is on estimating systematic uncertainties resulting\nfrom the interplay of energy loss fluctuations and the rapid increase of the\nparton transverse momentum slopes as sqrt{s} decreases from 200 to 62 AGeV.", "category": "nucl-th" }, { "text": "Structure of ground and excited states of $^{12}$C: We studied the ground and excited states of $^{12}$C based on variational\ncalculations after spin-parity projection in a framework of antisymmetrized\nmolecular dynamics(AMD). The calculations systematically reproduce various\nexperimental data. It was found that the sub-shell closure and SU(3)-limit\n$3\\alpha$ cluster components are contained in the ground state, while various\n$3\\alpha$ cluster structures develop in the excited states. We discussed\neffects of $\\alpha$ breaking and show the importance of coexistence of the\ncluster and shell-model-like aspects.", "category": "nucl-th" }, { "text": "Strongly Intensive Cumulants: Fluctuation Measures for Systems With\n Incompletely Constrained Volumes: The cumulants of thermal variables are of general interest in physics due to\ntheir extensivity and their correspondence with susceptibilities. They become\nespecially significant near critical points of phase transitions where they\ndiverge along with the correlation length. Cumulant measurements have been used\nextensively within the field of heavy-ion physics, principally as tools in the\nsearch for a hypothetical QCD critical point along the transition between\nhadronic matter and QGP. The volume of individual heavy-ion collisions can be\nonly partially constrained and, as a result, cumulant measurements are\nsignificantly biased by the limited volume resolution. We propose a class of\nmoments called strongly intensive cumulants which can be accurately measured in\nthe presence of unconstrained volume fluctuations. Additionally, they share the\nsame direct relationship with susceptibilities as cumulants in many cases.", "category": "nucl-th" }, { "text": "Determination of matter radius and neutron skin of $^{58}$Ni from\n reaction cross section of proton+$^{58}$Ni scattering based on chiral\n $g$-matrix model: Background: Using the chiral (Kyushu) $g$-matrix folding model with the\ndensities calculated with Gogny-HFB (GHFB) with the angular momentum projection\n(AMP), we determined the central values of matter radius and neutron skin from\nthe central values of reaction cross sections $\\sigma_{\\rm R}({\\rm EXP})$ of\np+$^{40,48}$Ca and p+$^{208}$Pb scattering. As for p+$^{58}$Ni scattering,\n$\\sigma_{\\rm R}({\\rm EXP})$ are available as a function of incident energy\n$E_{\\rm in}$. Aim: Our aim is to determine matter radius $r_{m}$ and skin\n$r_{\\rm skin}$ for $^{58}$Ni from the $\\sigma_{\\rm R}({\\rm EXP})$ of\np+$^{58}$Ni scattering by using the Kyushu $g$-matrix folding model with the\nGHFB+AMP densities. Results: For p+$^{58}$Ni scattering, the Kyushu $g$-matrix\nfolding model with the GHFB+AMP densities reproduces $\\sigma_{\\rm R}({\\rm\nEXP})$ in $8.8 \\leq E_{\\rm in} \\leq 81$MeV. For $E_{\\rm in}=81$MeV, we define\nthe factor $F$ as $F=\\sigma_{\\rm R}({\\rm EXP})/\\sigma_{\\rm R}({\\rm\nAMP})=0.9775$. The $F\\sigma_{\\rm R}({\\rm AMP})$ be much the same as the center\nvalues of $\\sigma_{\\rm R}({\\rm EXP})$ in $8.8 \\leq E_{\\rm in} \\leq 81$MeV. We\nthen determine $r_{\\rm m}({\\rm EXP})$ from the center values of $\\sigma_{\\rm\nR}({\\rm EXP})$, using $\\sigma_{\\rm R}({\\rm EXP})=C r_{m}^{2}({\\rm EXP})$ with\n$C=r_{m}^{2}({\\rm AMP})/ (F\\sigma_{\\rm R}({\\rm AMP}))$. The $r_{m}({\\rm EXP})$\nthus obtained are averaged over $E_{\\rm in}$. The averaged value is $r_{m}({\\rm\nEXP})=3.697$fm. Eventually, we obtain $r_{\\rm skin}({\\rm EXP})=0.023$fm from\n$r_{\\rm m}=3.697$fm and $r_p({\\rm EXP})=3.685$fm of electron scattering.", "category": "nucl-th" }, { "text": "A correlated model for lambda-hypernuclei: We study the properties of hypernuclei containing one lambda hyperon in the\nframework of the correlated basis function theory with Jastrow correlations.\nFermi hypernetted chain integral equations are derived and used to evaluate\nenergies and one-body densities of lambda hypernuclei having a doubly closed\nshell nucleonic core in the jj coupling scheme, from Carbon to Lead. We also\nstudy hypernuclei having the least bound neutron substituted by the lambda\nparticle. The semi-realistic Afnan and Tang nucleon-nucleon potential and\nBodmer and Usmani lambda-nucleon potential are adopted. The effect of many-body\nforces are considered by means either of a three body lambda-nucleon-nucleon\npotential of the Argonne type or of a density dependent modification of the\nlambda-nucleon interaction, fitted to reproduce the lambda binding energy in\nnuclear matter. While Jastrow correlations underestimate the attractive\ncontribution of the three body $\\la$ interaction, the density dependent\npotential provides a good description of the lambda binding energies over all\nthe nuclear masses range, in spite of the relative simplicity of the model.", "category": "nucl-th" }, { "text": "Indication of Collective Flow and Transparency in p-p Collisions at LHC: The mid-rapidity transverse momentum spectra of hadrons and the available\nrapidity distributions of the strange hadrons produced in p-p collisions at LHC\nenergy root(snn) = 0.9 TeV and root(snn)= 7.0 TeV have been studied using a\nunified statistical thermal freeze-out model. The calculated results are found\nto be in good agreement with the experimental data. The theoretical fits of the\ntransverse momentum spectra using the model calculations provide the thermal\nfreeze-out conditions in terms of the temperature and collective flow\nparameters for different hadronic species. The study reveal the presence of\nsignificant collective flow and a well defined temperature in the system thus\nindicating the formation of a thermally equilibrated hydrodynamic system in p-p\ncollisions at LHC. Moreover, the fits to the available experimental rapidity\ndistributions data of strange hadrons show the effect of almost complete\ntransparency in p-p collisions at LHC. The transverse momentum distributions of\nprotons and Kaons produced in p-p collisions at root(snn) = 200 GeV and\nroot(snn)= 2.76 TeV have also been reproduced successfully. The model\nincorporates longitudinal as well as a transverse hydrodynamic flow. The\ncontributions from heavier decay resonances have also been taken into account.\nWe have also imposed the criteria of exact strangeness conservation in the\nsystem.", "category": "nucl-th" }, { "text": "Symmetry energy from fragment observables in the canonical thermodynamic\n model: Different formulas relying measurable fragment isotopic observables to the\nsymmetry energy of excited nuclei have been proposed and applied to the\nanalysis of heavy ion collision data in the recent literature. In this paper we\nexamine the quality of the different expressions in the framework of the McGill\nCanonical Thermodynamic Model. We show that even in the idealized situation of\ncanonical equilibrium and in the absence of secondary decay, these formulas do\nnot give a precise reconstruction of the symmetry energy of the fragmenting\nsource. However, both isotopic widths and isoscaling appear very well\ncorrelated to the physical symmetry energy.", "category": "nucl-th" }, { "text": "Isovector deformation and its link to the neutron shell closure: DWBA analysis of the inelastic $^{30-40}$S$(p,p')$ and $^{18-22}$O$(p,p')$\nscattering data measured in the inverse kinematics has been performed to\ndetermine the isoscalar ($\\delta_0$) and isovector ($\\delta_1$) deformation\nlengths of the 2$^+_1$ excitations in the Sulfur and Oxygen isotopes using a\ncompact folding approach. A systematic $N$-dependence of $\\delta_0$ and\n$\\delta_1$ has been established which shows a link between $\\delta_1$ and the\nneutron-shell closure. Strong isovector deformations were found in several\ncases, e.g., the 2$^+_1$ state in $^{20}$O where $\\delta_1$ is nearly three\ntimes larger than $\\delta_0$. These results confirm the relation\n$\\delta_1>\\delta_0$ anticipated from the core polarization by the valence\nneutrons in the open-shell (neutron rich) nuclei. The effect of neutron shell\nclosure at N=14 or 16 has been discussed based on the folding model analysis of\nthe inelastic $^{22}$O+$p$ scattering data at 46.6 MeV/u measured recently at\nGANIL.", "category": "nucl-th" }, { "text": "Heavy quark(onium) at LHC: the statistical hadronization case: We discuss the production of charmonium in nuclear collisions within the\nframework of the statistical hadronization model. We demonstrate that the model\nreproduces very well the availble data at RHIC. We provide predictions for the\nLHC energy where, dependently on the charm production cross section, a\ndramatically different behaviour of charmonium production as a function of\ncentrality might be expected. We discuss also the case in elementary\ncollisions, where clearly the statistical model does not reproduce the\nmeasurements.", "category": "nucl-th" }, { "text": "Breakup of $^8$B and the $^7$Be($p,\u03b3)^8$B reaction: The calculated rate of events in some of the existing solar neutrino\ndetectors is directly proportional to the rate of the $^7$Be($p,\\gamma)^8$B\nreaction measured in the laboratory at low energies. However, the low-energy\ncross sections of this reaction are quite uncertain as various measurements\ndiffer from each other by 30-40 %. The Coulomb dissociation process which\nreverses the radiative capture by the dissociation of $^8$B in the Coulomb\nfield of a target, provides an alternate way of accessing this reaction. While\nthis method has several advantages (like large breakup cross sections and\nflexibility in the kinematics), the difficulties arise from the possible\ninterference by the nuclear interactions, uncertainties in the contributions of\nthe various multipoles and the higher order effects, which should be considered\ncarefully. We review the progress made so far in the experimental measurements\nand theoretical analysis of the breakup of $^8$B and discuss the current status\nof the low-energy cross sections (or the astrophysical $S$-factor) of the\n$^7$Be($p,\\gamma)^8$B reaction extracted therefrom. The future directions of\nthe experimental and theoretical investigations are also suggested.", "category": "nucl-th" }, { "text": "Breakup reactions of the halo nuclei Be11 and B8: We calculate the nuclear induced breakup of Be11 and B8 using a more\nrealistic treatment of the diffraction and stripping processes than in previous\nwork. The breakup is treated in the eikonal approximation with a profile\nfunction calculated from a realistic optical potential at low energies and from\nfree nucleon-nucleon cross sections at high energies. This treatment gives a\ngood description of measured breakup cross sections, as well as the\nlongitudinal momentum distribution of the core-like fragments, which is\nnarrower than predicted in the transparent limit. The real part of the\npotential is found to be significant and enhances the diffractive breakup at\nlow energies.", "category": "nucl-th" }, { "text": "Back-to-back relative-excess observable in search for the chiral\n magnetic effect: $\\textbf{Background:}$ The chiral magnetic effect (CME) is extensively\nstudied in heavy-ion collisions at RHIC and LHC. In the commonly used reaction\nplane (RP) dependent, charge dependent azimuthal correlator ($\\Delta\\gamma$),\nboth the close and back-to-back pairs are included. Many backgrounds contribute\nto the close pairs (e.g. resonance decays, jet correlations), whereas the\nback-to-back pairs are relatively free of those backgrounds.\n $\\textbf{Purpose:}$ In order to reduce those backgrounds, we propose a new\nobservable which only focuses on the back-to-back pairs, namely, the relative\nback-to-back opposite-sign (OS) over same-sign (SS) pair excess\n($r_{\\text{BB}}$) as a function of the pair azimuthal orientation with respect\nto the RP ($\\varphi_{\\text{BB}}$).\n $\\textbf{Methods:}$ We use analytical calculations and toy model simulations\nto demonstrate the sensitivity of $r_{\\text{BB}}(\\varphi_{\\text{BB}})$ to the\nCME and its insensitivity to backgrounds.\n $\\textbf{Results:}$ With finite CME, the $\\varphi_{\\text{BB}}$ distribution\nof $r_{\\text{BB}}$ shows a clear characteristic modulation. Its sensitivity to\nbackground is significantly reduced compared to the previous $\\Delta\\gamma$\nobservable. The simulation results are consistent with our analytical\ncalculations.\n $\\textbf{Conclusions:}$ Our studies demonstrate that the\n$r_{\\text{BB}}(\\varphi_{\\text{BB}})$ observable is sensitive to the CME signal\nand rather insensitive to the resonance backgrounds.", "category": "nucl-th" }, { "text": "Two neutrino double beta decay within the $\u03be$-approximation: We examine the contributions of odd-parity nuclear operators to the\ntwo-neutrino double beta decay $0^+\\rightarrow 0^+$ amplitude, which come from\nthe $P$-wave Coulomb corrections to the electron wave functions and the recoil\ncorrections to the nuclear currents. Although they are formally of higher order\nin $\\alpha Z/2$ or $v/c$ of the nucleon than the usual Fermi and Gamow-Teller\nmatrix elements, explicit calculations performed within the QRPA show that they\nare significant when confronted with the experimental data.", "category": "nucl-th" }, { "text": "First Excited 2+ Energy State Estimations of Even-even Nuclei by Using\n Artificial Neural Networks: The first excited 2+ energy states of nuclei give many substantial\ninformation related to the nuclear structure. Including these levels, all\nexcited states of nuclei are shown regularities in spin, parity and energy. In\nthe even-even nuclei, the first excited state is generally 2+ and the energy\nvalues of them increase as the closed shells are approached. The excited levels\nin nuclei can be investigated by using theoretical nuclear models such nuclear\nshell model. In the present study for the first time, we have used artificial\nneural networks for the determination of the energies of first 2+ states in the\neven-even nuclei in nuclidic chart as a function of Z, N and A numbers. We have\nused adopted literature values for the estimations. According to the results,\nthe method is convenient for this goal and one can confidently use the method\nfor the determination of first 2+ state energy values whose experimental values\ndo not exist in the literature.", "category": "nucl-th" }, { "text": "Bifurcation in kinetic equation for interacting Fermi systems: The finite duration of collisions appear as time-nonlocality in the kinetic\nequation. Analyzing the corresponding quantum kinetic equation for dense\ninteracting Fermi systems a delay differential equation is obtained which\ncombines time derivatives with finite time stepping known from the logistic\nmapping. The responsible delay time is explicitly calculated and discussed. As\na novel feature oscillations in the time evolution of the distribution function\nitself appear and bifurcations up to chaotic behavior can occur. The\ntemperature and density conditions are presented where such oscillations and\nbifurcations arise indicating an onset of phase transition.", "category": "nucl-th" }, { "text": "Recent developments in the constituent quark model including\n quark-antiquark pairs: We present the formalism for a new generation of unquenched quark models for\nbaryons in which the effects of quark-antiquark pairs (u anti-u, d anti-d and s\nanti-s) are taken into account in an explicit form via a microscopic,\nQCD-inspired, quark-antiquark creation mechaniscm. The present approach is an\nextension of the flux-tube breaking model of Geiger and Isgur in which now the\ncontributions of quark-antiquark pairs an be studied for any initial baryon and\nfor any flavor of the q anti-q pair. It is shown that the inclusion of q anti-q\nparis leads to a large contribution of orbital angular momentum to the proton\nspin.", "category": "nucl-th" }, { "text": "Analysis of Chiral Mean-Field Models for Nuclei: An analysis of nuclear properties based on a relativistic energy functional\ncontaining Dirac nucleons and classical scalar and vector meson fields is\ndiscussed. Density functional theory implies that this energy functional can\ninclude many-body effects that go beyond the simple Hartree approximation.\nUsing basic ideas from effective field theory, a systematic truncation scheme\nis developed for the energy functional, which is based on an expansion in\npowers of the meson fields and their gradients.\n Chiral models are analyzed by considering specific lagrangians that realize\nthe spontaneously broken chiral symmetry of QCD in different ways and by\nstudying them at the Hartree level. Models that include a light scalar meson\nplaying a dual role as the chiral partner of the pion and the mediator of the\nintermediate-range nucleon-nucleon interaction, and which include a\n\"Mexican-hat\" potential, fail to reproduce basic ground-state properties of\nnuclei. In contrast, chiral models with a nonlinear realization of the symmetry\nare shown to contain the full flexibility inherent in the general energy\nfunctional and can therefore successfully describe nuclei.", "category": "nucl-th" }, { "text": "Fusion rates in nuclear plasmas: Energy and momentum of the elementary excitations become independent\nvariables in medium: energy and momentum statistical distributions are not\nidentical. The momentum distribution and not the energy distribution is\nrelevant for barrier penetration. The deviations of the momentum distribution\nfrom the Maxwell-Boltzmann energy distribution can be expressed in terms of the\nimaginary part of the self-energy of the quasi-particle. It is possible to\nobtain an effective Tsallis' distribution for the kinetic energy. These effects\nare different from static or dynamical screening and can have important\nconsequences for reaction rates in stars.", "category": "nucl-th" }, { "text": "Hindered alpha decays of heaviest high-K isomers: To find candidates for long-lived high-K isomers in even-even Z=106-112\nsuperheavy nuclei we study dominant alpha-decay channel of two- and\nfour-quasi-particle configurations at a low excitation. Energies are calculated\nwithin the microscopic - macroscopic approach with the deformed Woods-Saxon\npotential. Configurations are fixed by a standard blocking procedure and their\nenergy found by a subsequent minimization over deformations. Different\nexcitation energies of a high-K configuration in parent and daughter nucleus\nseem particularly important for a hindrance of the alpha-decay. A strong\nhindrance is found for some four-quasi-particle states, particularly $K^{\\pi} =\n20^{+}$ and/or $19^{+}$ states in $^{264-270}$Ds. Contrary to what was\nsuggested in experimental papers, it is rather a proton configuration that\nleads to this strong hindrance. If not shortened by the electromagnetic decay,\nalpha half-lives of $\\sim$ 1 s could open new possibilities for studies of\nchemical/atomic properties of related elements.", "category": "nucl-th" }, { "text": "A model for nuclear matter fragmentation: phase diagram and cluster\n distributions: We develop a model in the framework of nuclear fragmentation at thermodynamic\nequilibrium which can be mapped onto an Ising model with constant\nmagnetization. We work out the thermodynamic properties of the model as well as\nthe properties of the fragment size distributions. We show that two types of\nphase transitions can be found for high density systems. They merge into a\nunique transition at low density. An analysis of the critical exponents which\ncharacterize observables for different densities in the thermodynamic limit\nshows that these transitions look like continuous second order transitions.", "category": "nucl-th" }, { "text": "Single and double pi^{-}/pi^{+} ratios in heavy-ion reactions as probes\n of the high-density behavior of the nuclear symmetry energy: Based on an isospin- and momentum-dependent hadronic transport model IBUU04,\neffects of the nuclear symmetry energy on the single and double\npi^{-}/pi^{+}ratios in central reactions of ^{132}Sn+^{124}Sn and\n^{112}Sn+^{112}Sn at a beam energy of 400 MeV/nucleon are studied. It is found\nthat around the Coulomb peak of the single pi^{-}/pi^{+} ratio the double\npi^{-}/pi^{+} ratio taken from the two isotopic reactions retains about the\nsame sensitivity to the density dependence of nuclear symmetry energy. Because\nthe double pi^{-}/pi^{+}ratio can reduce significantly the systematic errors,\nit is thus a more effective probe for the high-density behavior of the nuclear\nsymmetry energy.", "category": "nucl-th" }, { "text": "Landau-Ginzburg method applied to finite fermion systems: Pairing in\n Nuclei: Given the spectrum of a Hamiltonian, a methodology is developed which employs\nthe Landau-Ginsburg method for characterizing phase transitions in infinite\nsystems to identify phase transition remnants in finite fermion systems. As a\nfirst application of our appproach we discuss pairing in finite nuclei.", "category": "nucl-th" }, { "text": "Nonperturbative QCD Phenomenology and Light Quark Physics: Recent progress in modeling QCD for hadron physics through truncated\nDyson-Schwinger equations is reviewed. Special emphasis is put upon comparison\nof dressed quark propagators and the dressed quark-gluon vertex with\nlattice-QCD results.", "category": "nucl-th" }, { "text": "Uncertainties in nuclear transition matrix elements for neutrinoless\n $\u03b2\u03b2$ decay within the PHFB model: The nuclear transition matrix elements $M^{(0\\nu)}$ for the neutrinoless\ndouble beta decay of $^{94,96}$Zr, $^{98,100}$Mo, $^{104}$Ru, $^{110}$Pd,\n$^{128,130}$Te and $^{150}$Nd isotopes in the case of $0^{+}\\rightarrow 0^{+}$\ntransition are calculated using the PHFB wave functions, which are eigenvectors\nof four different parameterizations of a Hamiltonian with pairing plus\nmultipolar effective two-body interaction. \\QCOM{35}{In addition, the\nconsideration of} Employing two (three) different parameterizations of\nJastrow-type short range correlations, \\QCOM{19}{provides us with} a set of\neight (twelve) different nuclear transition matrix elements $M^{(0\\nu)}$ is\nbuilt for each decay, whose averages in conjunction with their standard\ndeviations provide an estimate of the model uncertainties.", "category": "nucl-th" }, { "text": "SU(2) Chiral sigma model and the properties of neutron stars: We discuss the {\\it SU}(2) chiral sigma model in the context of nuclear\nmatter using a mean field approach at high density. In this model we include a\ndynamically generated isoscalar vector field and higher-order terms in the\nscalar field. With the inclusion of these, we reproduce the empirical values of\nthe nuclear matter saturation density, binding energy, and nuclear\nincompressibility. The value of the incompressibility is chosen according to\nrecently obtained heavy-ion collision data. We then apply the same dynamical\nmodel to neutron-rich matter in beta equilibrium, related to neutron star\nstructure. The maximum mass and corresponding radius of stable non-rotating\nneutron stars are found to be in the observational limit.", "category": "nucl-th" }, { "text": "The Non-perturbative Interaction of the Pseudovector Coupling for the\n Pion-nucleon Scattering: The effect of the non-perturbative term is investigated for the pion-nucleon\nscattering. Including the self-energy of nucleon the cross section of the\nelastic scattering results in a constant value at the laboratory momentum $p_L\n\\to \\infty$. The amplitude of the forward direction is applied to the\ndispersion relation.", "category": "nucl-th" }, { "text": "Formation Of Quark Matter In Neutron Stars: At very large densities and/or temperatures a quark-hadron phase transition\nis expected to take place. Simulations of QCD on lattice at zero baryon density\nindicate that the transition occurs at $T_c \\sim 150-170$ MeV. The calculations\nindicate that transition is likely to be second order or a cross over\nphenomenon. Although the lattice simulations have not given any indication on\nwhen the transition occurs at nonzero baryon density, the transition is\nexpected to occur around the densities of few times nuclear matter density.\nAlso, there is a strong reason to believe that the quark matter formed after\nthe phase transition is in colour superconducting phase. The matter densities\nin the interior of neutron stars are expected to be several times the nuclear\nmatter density and therefore the neutron star cores may possibly consist of\nquark matter. One then expects that this quark matter is formed during the\ncollapse of supernova. Starting with the assumption that the quark matter, when\nformed consists of predominantly u and d quarks, we consider the evolution of\nstrange quarks by weak interactions in the present work. The reaction rates and\ntime required to reach the chemical equilibrium are computed here. Our\ncalculations show that the chemical equilibrium is reached in about $10^{-7}$\nseconds. Further more during and immediately after the equilibration process\nenormous amount of energy is released and copious numbers of neutrinos are\nproduced. We show that for reasonable models of nuclear equations of state the\namount of energy released could be as high as $10^{53}$ ergs and as many as\n$10^{58}$ neutrinos may be emitted during the quark matter formation.", "category": "nucl-th" }, { "text": "The anatomy of the simplest Duflo-Zuker mass formula: The simplest version of the Duflo-Zuker mass model (due entirely to the late\nJean Duflo) is described by following step by step the published computer code.\nThe model contains six macroscopic monopole terms leading asymptotically to a\nLiquid Drop form, three microscopic terms supposed to mock configuration mixing\n(multipole) corrections to the monopole shell effects, and one term in charge\nof detecting deformed nuclei and calculating their masses. A careful analysis\nof the model suggests a program of future developments that includes a\ncomplementary approach to masses based on an independently determined monopole\nHamiltonian, a better description of deformations and specific suggestions for\nthe treatment of three body forces.", "category": "nucl-th" }, { "text": "Hyperspherical cluster model for bosons: application to sub-threshold\n halo states in helium drops: To describe long-range behaviour of one particle removed from a few- or a\nmany-body system, a hyperspherical cluster model has been developed. It has\nbeen applied to the ground and first excited states of helium drops with five,\nsix, eight and ten atoms interacting via a two-body soft gaussian potential.\nConvergence of the hyperspherical cluster harmonics expansion is studied for\nbinding energies, root-mean-squared radii and overlaps of the wave functions of\ntwo helium drops differing by one atom. It was shown that with increasing model\nspace the functional form of such overlaps at large distances converges to the\ncorrect asymptotic behaviour. The asymptotic normalization coefficients that\nquantify the overlaps' amplitudes in this region are calculated. It was also\nshown that in the first excited state one helium atom stays far apart from the\nrest forming a two-body molecule, or a halo. The probability of finding the\nhalo atom in the classically-forbidden region of space depends on the\ndefinition of the latter and on the number of atoms in the drop. The total norm\nof the overlap integrals, the spectroscopic factor, represents the number of\npartitions of a many-body state into a chosen state of the system with one\nparticle removed. The spectroscopic factors have been calculated and their sum\nrules are discussed giving a further insight into the structure of helium\ndrops.", "category": "nucl-th" }, { "text": "Isospin Properties of ($K^-$, $N$) Reactions for the Formation of\n Deeply-bound Antikaonic Nuclei: The formation of deeply-bound antikaonic $K^-/\\bar{K}^0$ nuclear states by\nnuclear ($K^-$, $N$) reactions is investigated theoretically within a\ndistorted-wave impulse approximation (DWIA), considering the isospin properties\nof the Fermi-averaged $K^-+ N \\to N + \\bar{K}$ elementary amplitudes. We\ncalculate the formation cross sections of the deeply-bound $\\bar{K}$ states by\nthe ($K^-$, $N$) reactions on the nuclear targets, $^{12}$C and $^{28}$Si, at\nincident $K^-$ lab momentum $p_{K^-}$ = 1.0 GeV/c and $\\theta_{\\rm lab} =\n0^{\\circ}$, introducing a complex effective nucleon number $N_{\\rm eff}$ for\nunstable bound states in the DWIA. The results show that the deeply-bound\n$\\bar{K}$ states can be populated dominantly by the ($K^-$, $n$) reaction via\nthe total isoscalar $\\Delta T=0$ transition owing to the isospin nature of the\n$K^-+ N \\to N + \\bar{K}$ amplitudes, and that the cross sections described by\n${\\rm Re}N_{\\rm eff}$ and ${\\rm Arg}N_{\\rm eff}$ enable to deduce the structure\nof the $\\bar{K}$ nuclear states; the calculated inclusive nucleon spectra for a\ndeep $\\bar{K}$-nucleus potential do not show distinct peak structure in the\nbound region. The few-body $\\bar{K}\\otimes [NN]$ and $\\bar{K}\\otimes [NNN]$\nstates formed in ($K^-$, $N$) reactions on $s$-shell nuclear targets, $^3$He,\n$^3$H and $^4$He, are also discussed.", "category": "nucl-th" }, { "text": "Extracting meson-baryon contributions to the electroexcitation of the\n $N(1675){\\frac{5}{2}}^-$ nucleon resonance: We report on the determination of the electrocouplings for the transition\nfrom the proton to the $N(1675){\\frac{5}{2}}^-$ resonance state using recent\ndifferential cross section data on $e p \\rightarrow e\\pi^+ n$ by the CLAS\ncollaboration at $1.8 \\le Q^2 < 4.5$GeV$^2$. The data have been analyzed using\ntwo different approaches, the unitary isobar model and fixed-t dispersion\nrelations. The extracted $\\gamma^* p\\rightarrow N(1675){\\frac{5}{2}}^-$\nhelicity amplitudes show considerable coupling through the $A^p_{1/2}$\namplitude, that is significantly larger than predicted three-quark contribution\nto this amplitude. The amplitude $A^p_{3/2}$ is much smaller. Both results are\nconsistent with the predicted sizes of the meson-baryon contributions at $Q^2\n\\geq 1.8 $GeV$^2$ from the dynamical coupled-channel model.", "category": "nucl-th" }, { "text": "Dynamical and sequential decay effects on isoscaling and density\n dependence of the symmetry energy: The isoscaling properties of the primary and final products are studied via\nisospin dependent quantum molecular dynamics\n (IQMD) model and the followed sequential decay model GEMINI, respectively. It\nis found that the isoscaling parameters $\\alpha$ of both primary and final\nproducts keep no significant change for light fragments, but increases with the\nmass for intermediate and heavy products. The dynamical effects on isoscaling\nare exhibited by that $\\alpha$ value decreases a little with the evolution time\nof the system, and opposite trend for the heavy products. The secondary decay\neffects on isoscaling are reflected in the increasing of the $\\alpha$ value for\nthe final products which experiences secondary decay process.\n Furthermore the density dependence of the symmetry energy has also been\nexplored, it is observed that in the low densities the symmetry energy\ncoefficient has the form of $C_{sym}(\\rho)\\sim C_{0}(\\rho/\\rho_{0})^{\\gamma}$,\nwhere $\\gamma = 0.7 \\sim 1.3$ for both primary and final products, but $C_{0}$\nhave different values for primary and final products. It is also suggested that\nit might be more reasonable to describe the density dependence of the symmetry\nenergy coefficient by the $C_{sym}(\\rho/\\rho_{0})\\approx\nC_{1}(\\rho/\\rho_{0})^{\\gamma_{soft}} + C_{2}(\\rho/\\rho_{0})^{\\gamma_{stiff}}$\nwith $\\gamma_{soft}\\leq 1$, $\\gamma_{stiff}\\geq 1$ and $C_{1}, C_{2}$ constant\nparameters.", "category": "nucl-th" }, { "text": "Improving proton-induced one-nucleon removal in intranuclear cascade: It is a well-established fact that intranuclear-cascade models generally fail\nto consistently reproduce the cross sections for one-proton and one-neutron\nremoval from stable nuclei by a high-energy proton beam. We use simple\nshell-model calculations to investigate the reasons of this deficiency. We find\nthat a refined description of the neutron skin and of the energy density in the\nnuclear surface is crucial for the aforementioned observables, and that neither\ningredient is sufficient if taken separately. As a by-product, the predictions\nfor removal of several nucleons are also improved by the refined treatment.", "category": "nucl-th" }, { "text": "Compressional properties of nuclear matter in the relativistic mean\n field theory with the excluded volume effects: Compressional properties of nuclear matter are studied by using the mean\nfield theory with the excluded volume effects of the nucleons. It is found that\nthe excluded volume effects make it possible to fit the empirical data of the\nCoulomb coefficient $K_{c}$ of nucleus incompressibility, even if the volume\ncoefficient $K$ is small($\\sim 150$MeV). However, the symmetry properties favor\n$K=300\\pm 50$MeV as in the cases of the mean field theory of point-like\nnucleons.", "category": "nucl-th" }, { "text": "Mass asymmetry effects on geometry of vanishing flow: Mass asymmetry effects on geometry of vanishing flow.", "category": "nucl-th" }, { "text": "Net-proton number fluctuations in the presence of the QCD critical point: Event-by-event fluctuations of the net-proton number studied in heavy-ion\ncollisions provide an important means in the search for the conjectured\ncritical end point (CP) in the QCD phase diagram. We propose a phenomenological\nmodel in which the fluctuations of the chiral critical mode couple to protons\nand anti-protons. This allows us to study the behavior of the net-proton number\nfluctuations in the presence of the CP. Calculating the net-proton number\ncumulants, $C_n$ with n=1,2,3,4, along the phenomenological freeze-out line we\nshow that the ratio of variance and mean $C_2/C_1$, as well as kurtosis\n$C_4/C_2$ resemble qualitative properties observed in data in heavy-ion\ncollisions as a function of beam energy obtained by the STAR Collaboration at\nRHIC. In particular, the non-monotonic structure of the kurtosis and smooth\nchange of the $C_2/C_1$ ratio with beam energy could be due to the CP located\nnear the freeze-out line. The skewness, however, exhibits properties that are\nin contrast to the criticality expected due to the CP. The dependence of our\nresults on the model parameters and the proximity of the chemical freeze-out to\nthe critical point are also discussed.", "category": "nucl-th" }, { "text": "Role of non-gaussian quantum fluctuations in neutrino entanglement: The flavor evolution of neutrinos in environments with large neutrino number\ndensities is an open problem at the nexus of astrophysics and neutrino flavor\nphysics. Among the many unanswered questions pertaining to this problem, it\nremains to be determined whether neutrino-neutrino coherent scattering can give\nrise to nontrivial quantum entanglement among neutrinos, and whether this can\naffect the flavor evolution in a meaningful way. To gain further insight into\nthis question, here we study a simple system of two interacting neutrino beams,\nand obtain the exact phase-space explored by this system using the Husimi\nquasi-probability distribution. We observe that the entanglement induced by the\ncoupling leads to strong delocalization in phase-space with largely\nnon-Gaussian quantum fluctuations. The link between the neutrino entanglement\nand quantum fluctuations is illustrated using the one- and two-neutrino\nentropy. In addition, we propose an approximate phase-space method to describe\nthe interacting neutrinos problem, where the exact evolution is replaced by a\nset of independent mean-field evolutions with a statistical sampling of the\ninitial conditions. The phase-space approach provides a simple and accurate\nmethod to describe the gross features of the neutrino entanglement problem.\nApplications are shown using time-independent and time-dependent Hamiltonians\nin the non-adiabatic regime.", "category": "nucl-th" }, { "text": "On the structure in the $\u039bN$ cross section at the $\u03a3N$\n threshold: The complexity of threshold phenomena is exemplified on a prominent and\nlong-known case - the structure in the $\\Lambda p$ cross section (invariant\nmass spectrum) at the opening of the $\\Sigma N$ channel. The mass splitting\nbetween the $\\Sigma$ baryons together with the angular momentum coupling in the\n$^3S_1$-$^3D_1$ partial wave imply that, in principle, up to six channels are\ninvolved. Utilizing hyperon-nucleon potentials that provide an excellent\ndescription of the available low-energy $\\Lambda p$ and $\\Sigma N$ scattering\ndata, the shape of the resulting $\\Lambda p$ cross section is discussed and the\npoles near the $\\Sigma N$ threshold are determined. Evidence for a strangeness\n$S=-1$ dibaryon is provided, in the form of a deuteron-like (unstable) $\\Sigma\nN$ bound state. Predictions for level shifts and widths of $\\Sigma^-p$ atomic\nstates are given.", "category": "nucl-th" }, { "text": "Nonperturbative Quantum Field Evolution: We introduce a nonperturbative, first-principles approach to time-dependent\nproblems in quantum field theory. In this approach, the time-evolution of\nquantum field configurations is calculated in real time and at the amplitude\nlevel. This method is particularly suitable for treating systems interacting\nwith a time-dependent background field. As a test problem, we apply this\napproach to QED and study electron acceleration and the associated photon\nemission in a time- and space-dependent electromagnetic background field.", "category": "nucl-th" }, { "text": "A Monte Carlo approach to study neutron and fragment emission in\n heavy-ion reactions: Quantum Molecular Dynamics models (QMD) are Monte Carlo approaches targeted\nat the description of nucleon-ion and ion-ion collisions. We have developed a\nQMD code, which has been used for the simulation of the fast stage of ion-ion\ncollisions, considering a wide range of system masses and system mass\nasymmetries. The slow stage of the collisions has been described by statistical\nmethods. The combination of both stages leads to final distributions of\nparticles and fragments, which have been compared to experimental data\navailable in literature. A few results of these comparisons, concerning neutron\ndouble-differential production cross-sections for C, Ne and Ar ions impinging\non C, Cu and Pb targets at 290 - 400 MeV/A bombarding energies and fragment\nisotopic distributions from Xe + Al at 790 MeV/A, are shown in this paper.", "category": "nucl-th" }, { "text": "Density-dependent effective nucleon-nucleon interaction from chiral\n three-nucleon forces: We derive density-dependent corrections to the in-medium nucleon-nucleon\ninteraction from the leading-order chiral three-nucleon force. To this order\nthere are six distinct one-loop diagrams contributing to the in-medium\nnucleon-nucleon scattering T-matrix. Analytic expressions are presented for\neach of these in both isospin-symmetric nuclear matter as well as nuclear\nmatter with a small isospin asymmetry. The results are combined with the\nlow-momentum nucleon-nucleon potential V(low-k) to obtain an effective\ndensity-dependent interaction suitable for nuclear structure calculations. The\nin-medium interaction is decomposed into partial waves up to orbital angular\nmomentum L = 2. Our results should be particularly useful in calculations where\nan exact treatment of the chiral three-nucleon force would otherwise be\ncomputationally prohibitive.", "category": "nucl-th" }, { "text": "Emergence of low-energy monopole strength in the neutron-rich calcium\n isotopes: The isoscalar monopole response of neutron-rich nuclei is sensitive to both\nthe incompressibility coefficient of symmetric nuclear matter and the density\ndependence of the symmetry energy. The main goal of this paper is to explore\nthe emergence, evolution, and origin of low energy monopole strength along the\neven-even calcium isotopes: from 40Ca to 60Ca. The distribution of isoscalar\nmonopole strength is computed in a relativistic random phase approximation\n(RPA) using three effective interactions that have been calibrated to the\nproperties of finite nuclei and neutron stars. A non-spectral approach is\nadopted that allows for an exact treatment of the continuum without any\nreliance on discretization. For the stable calcium isotopes, no evidence of\nlow-energy monopole strength is observed, even as the 1f7/2 neutron orbital is\nbeing filled and the neutron-skin thickness progressively grows. Further, in\ncontrast to experimental findings, a mild softening of the monopole response\nwith increasing mass number is predicted. Beyond 48Ca, a significant amount of\nlow-energy monopole strength emerges as soon as the weak-binding neutron\norbitals (2p and 1f5/2) become populated. The emergence and evolution of\nlow-energy strength is identified with transitions from these weakly-bound\nstates into the continuum. Moreover, given that models with a soft symmetry\nenergy tend to reach the neutron-drip line earlier than their stiffer\ncounterparts, we identify an inverse correlation between the neutron-skin\nthickness and the inverse energy weighted sum.", "category": "nucl-th" }, { "text": "Near threshold laser-modified proton emission in nuclear photoeffect: The change of the probability of proton emission in nuclear photoeffect due\nto an intense coherent (laser) field is discussed near the threshold, where the\nhindering effect of the Coulomb field of the remainder nucleus is essential.\nThe ratio of laser-assisted and laser free differential cross section is\ndeduced and found to be independent of the polarization state of the $\\gamma $\nfield and the two types of initial nuclear state considered. The numerical\nvalues of this ratio are given at some characteristic parameters of the intense\nfield.", "category": "nucl-th" }, { "text": "Infinite-cutoff renormalization of the chiral nucleon-nucleon\n interaction at N3LO: Naively, the \"best\" method of renormalization is the one where a momentum\ncutoff is taken to infinity while maintaining stable results due to a\ncutoff-dependent adjustment of counterterms. We have applied this\nrenormalization method in the non-perturbative calculation of phase-shifts for\nnucleon-nucleon (NN) scattering using chiral NN potentials up to\nnext-to-next-to-next-to-leading order (N3LO). For lower partial waves, we find\nthat there is either no convergence with increasing order or, if convergence\noccurs, the results do not always converge to the empirical values. For higher\npartial waves, we always observe convergence to the empirical phase shifts\n(except for the 3G5 state). Furthermore, no matter what the order is, one can\nuse only one or no counterterm per partial wave, creating a rather erratic\nscheme of power counting that does not allow for a systematic order-by-order\nimprovement of the predictions. The conclusion is that infinite-cutoff\nrenormalization is inappropriate for chiral NN interactions, which should not\ncome as a surprise, since the chiral effective field theory, these interactions\nare based upon, is designed for momenta below the chiral-symmetry breaking\nscale of about 1 GeV. Therefore, this value for the hard scale should also be\nperceived as the appropriate upper limit for the momentum cutoff.", "category": "nucl-th" }, { "text": "Origin of the structures observed in $e^+e^-$ annihilation into\n multipion states around the $\\bar pp$ threshold: We analyze the origin of the structures observed in the reactions $e^+e^-\\to\n3(\\pi^+\\pi^-)$, $2(\\pi^+\\pi^-\\pi^0)$, $\\omega\\pi^+\\pi^-\\pi^0$, and $e^+e^-\\to\n2(\\pi^+\\pi^-)\\pi^0$ around the antiproton-proton ($\\bar pp$) threshold. We\ncalculate the contribution of the two-step process $e^+e^-\\to \\bar NN \\to$\nmultipions to the total reaction amplitude. The amplitude for $e^+e^-\\to \\bar\nNN$ is constrained from near-threshold data on the $e^+e^-\\to \\bar pp$ cross\nsection and the one for $\\bar NN \\to$ multipions can be likewise fixed from\navailable experimental information, for all those $5 \\pi$ and $6\\pi$ states.\nThe resulting amplitude for $e^+e^-\\to$ multipions turns out to be large enough\nto play a role for the considered $e^+e^-$ annihilation channels and, in three\nof the four reactions, even allows us to reproduce the data quantitatively near\nthe $\\bar NN$ threshold. The structures seen in the experiments emerges then as\na threshold effect due to the opening of the $\\bar NN$ channel.", "category": "nucl-th" }, { "text": "The basic K nuclear cluster K- pp and its enhanced formation in the p +\n p -> K+ + X reaction: We have studied the structure of K- pp nuclear cluster comprehensively by\nsolving this three-body system exactly in a variational method starting from\nthe Ansatz that the Lambda(1405) resonance (Lambda*) is a K-p bound state. We\nhave found that our original prediction for the presence of K-pp as a compact\nbound system with M = 2322$ MeV/c2, B = 48 MeV and Gamma = 60 MeV remains\nunchanged by varying the Kba-rN and NN interactions widely as far as they\nreproduce Lambda(1405). The structure of K- pp reveals a molecular feature,\nnamely, the K- in Lambda* as an \"atomic center\" plays a key role in producing\nstrong covalent bonding with the other proton. We have shown that the\nelementary process, p + p -> K+ + Lambda* + p, which occurs in a short impact\nparameter and with a large momentum transfer (Q ~ 1.6$ GeV/c), leads to\nunusually large self-trapping of Lambda* by the participating proton, since the\nLambda*-p system exists as a compact doorway state propagating to K- pp\n(R{Lambda*-p} ~ 1.67 fm).", "category": "nucl-th" }, { "text": "Double beta decay in heavy deformed nuclei: what have we learned?: The pseudo SU(3) approach is used to describe low lying states and BE(2)\nintensities of rare earth and actinide nuclei which are double beta decay\ncandidates. The double beta half lives of some of these nuclei to the ground\nand excited states of the final ones are evaluated for both the two and zero\nneutrino emitting modes. The existence of selection rules which strongly\nrestrict the decays is discussed. These restrictions represent a possible test\nof the model. Up to now the predictions are in good agreement with the\navailable experimental data.", "category": "nucl-th" }, { "text": "Relaxation time ansatz and shear and bulk viscosities of gluon matter: Shear and bulk viscosity-to-entropy density ratios are calculated for the\npure gluon matter in a non-equilibrium mean-field quasiparticle approach within\nthe relaxation time approximation. We study how different approximations used\nin the literature affect the results for the shear and bulk viscosities. Though\nthe results for the shear viscosity turned out to be quite robust, all\nevaluations of the shear and bulk viscosities obtained in the framework of the\nrelaxation time approximation can be considered only as rough estimations.", "category": "nucl-th" }, { "text": "Estimate of the location of the neutron drip line for calcium isotopes\n from an exact Hamiltonian with continuum pair correlations: The eastern region of the calcium isotope chain of the nuclei chart is,\nnowadays, of great activity. The experimental assessment of the limit of\nstability is of interest to confirm or improve microscopic theoretical models.\nThe goal of this work is to provide the drip line of the calcium isotopes from\nthe exact solution of the pairing Hamiltonian which incorporates explicitly the\ncorrelations with the continuum spectrum of energy. The modified Richardson\nequations, which include correlations with the continuum spectrum of energy\nmodeled by the continuum single particle level density, is used to solve the\nmany-body system. Three models are used, two isospin independent models with\ncore 40Ca and 48Ca, and one isospin dependent model. One and two-neutron\nseparation energies and occupation probabilities for bound and continuum states\nare calculated from the solution of the Richardson equations. The one particle\ndrip line is found at the nucleus 57Ca, while the two neutron drip line is\nfound at the nucleus 60Ca from the isospin independent model and at 66Ca from\nthe isospin dependent one.", "category": "nucl-th" }, { "text": "A New Topological \"Twist\" to BR Scaling: When vector mesons are considered on the same footing as pions as suggested\nby hidden local symmetry, the property of the nuclear tensor forces is strongly\ncontrolled by the behavior of the vector mesons in dense medium. This led to BR\nscaling in 1991. When baryons as skyrmions are put on crystal, there can be a\nphase transition from skyrmions to half-skyrmions at a density above that of\nnormal nuclear matter. This topology change can induce fundamental changes to\nthe parameters in hidden local symmetric Lagrangian, hence BR scaling, and\nbrings a drastic modification to the structure of nuclear forces, in\nparticulrar, the tensor forces. This can have far-reaching consequences on the\nEoS of compact-star matter and the structure of neutron-rich nuclei.", "category": "nucl-th" }, { "text": "From quark and nucleon correlations to discrete symmetry and clustering\n in nuclei: Starting with a quark model of nucleon structure in which the valence quarks\nare strongly correlated within a nucleon, the light nuclei are constructed by\nassuming similar correlations of the quarks of neighboring nucleons. Applying\nthe model to larger collections of nucleons reveals the emergence of the\nface-centered cubic (FCC) symmetry at the nuclear level. Nuclei with closed\nshells possess octahedral symmetry. Binding of nucleons are provided by quark\nloops formed by three and four nucleon correlations. Quark loops are\nresponsible for formation of exotic (borromean) nuclei, as well. The model\nunifies independent particle (shell) model, liquid-drop and cluster models.", "category": "nucl-th" }, { "text": "Refractive Distortions of Two-Particle Correlations: Using optical model calculations it has recently been shown that refractive\nphenomena from the collective mean field can significantly alter the sizes\ninferred from two-pion correlations. We demonstrate that such effects can be\naccounted for in classical calculations if mean field effects are included.", "category": "nucl-th" }, { "text": "Hot and Dense Matter Equation of State Probability Distributions for\n Astrophysical Simulations: We add an ensemble of nuclei to the equation of state for homogeneous\nnucleonic matter to generate a new set of models suitable for astrophysical\nsimulations of core-collapse supernovae and neutron star mergers. We implement\nempirical constraints from (i) nuclear mass measurements, (ii) proton-proton\nscattering phase shifts, and (iii) neutron star observations. Our model is also\nguided by microscopic many-body theory calculations based on realistic nuclear\nforces, including the zero-temperature neutron matter equation of state from\nquantum Monte Carlo simulations and thermal contributions to the free energy\nfrom finite-temperature many-body perturbation theory. We ensure that the\nparameters of our model can be varied while preserving thermodynamic\nconsistency and the connection to experimental or observational data, thus\nproviding a probability distribution of the astrophysical hot and dense matter\nequation of state. We compare our results with those obtained from other\navailable equations of state. While our probability distributions indeed\nrepresent a large number of possible equations of state, we cannot yet claim to\nhave fully explored all of the uncertainties, especially with regard to the\nstructure of nuclei in the hot and dense medium.", "category": "nucl-th" }, { "text": "J/\u03a8production, $\u03c7$ polarization and Color Fluctuations: The hard contributions to the heavy quarkonium-nucleon cross sections are\ncalculated based on the QCD factorization theorem and the nonrelativistic\nquarkonium model. We evaluate the nonperturbative part of these cross sections\nwhich dominates at $\\sqrt{s_{NN}}\\approx 20$ GeV at the Cern Super Proton\nSynchrotron (SPS) and becomes a correction at $\\sqrt{s_{NN}}\\approx 6$ TeV at\nthe CERN Large Hadron Collider (LHC). $\\J$ production at the CERN SPS is well\ndescribed by hard QCD, when the larger absorption cross sections of the $\\chi$\nstates predicted by QCD are taken into account. We predict an $A$-dependent\npolarization of the $\\chi$ states. The expansion of small wave packets is\ndiscussed.", "category": "nucl-th" }, { "text": "Particle production from off-shell nucleons: Particle production in equilibrium and nonequilibrium quantum systems is\ncalculated. The effects of the off-shell propagation of nucleons in medium on\nthe particle production are discussed. Comparision to the semiclassical\nproduction rate is given.", "category": "nucl-th" }, { "text": "Effect of the Quark-Gluon Vertex on Dynamical Chiral Symmetry Breaking: In this work, we investigate how the details of the quark-gluon interaction\nvertex affect the quantitative description of chiral symmetry breaking through\nthe gap equation for quarks. We start from two gluon propagator models widely\nused in literature and constructed in direct connection with our gradually\nimproved understanding of infrared quantum chromodynamics coupled with its\nexact one-loop limit. The gap equation is then solved by employing a variety of\nvertex \\emph{Ans\\\"atze}, which have been constructed in order to implement some\nof the key aspects of quantum chromodynamics, namely, multiplicative\nrenormalizability of the quark propagator, gauge invariance, matching with\nperturbation theory in the weak coupling regime, independence from unphysical\nkinematic singularities as well as manifestly correct transformation properties\nunder charge conjugation and parity operations. On general grounds, all\ntruncation schemes exhibit the same qualitative and quantitative pattern of\nchiral symmetry breaking, ensuring the overall robustness of this approach and\nits potentially reliable description of the hadron spectrum and properties.", "category": "nucl-th" }, { "text": "Dynamical coupled-channel study of K+ Lambda photoproduction: Results for the reaction gamma p --> K+ Lambda, studied within a constituent\nquark model and a dynamical coupled-channel approach, are presented and\ncompared with recent data. Issues related to the search for missing baryon\nresonances are briefly discussed and the role played by a third S_{11}\nresonance is underlined.", "category": "nucl-th" }, { "text": "Microscopic in-medium nucleon-nucleon cross sections with improved Pauli\n blocking effects: We present updated predictions of effective elastic nucleon-nucleon cross\nsections intended for use in nucleus-nucleus reactions. A novel characteristic\nof the present approach combines all microscopic medium effects included in the\nDirac-Brueckner-Hartree-Fock G-matrix with a Pauli blocking mechanism which is\nmore appropriate for applications in ion-ion reaction models as compared to a\nprevious approach. The effective in-medium cross section is found to be quite\nsensitive to the description of Pauli blocking in the final configurations.", "category": "nucl-th" }, { "text": "Gamow-Teller GT+ distributions in nuclei with mass A=90-97: We investigate the Gamow-Teller strength distributions in the\nelectron-capture direction in nuclei having mass A=90-97, assuming a 88Sr core\nand using a realistic interaction that reasonably reproduces nuclear\nspectroscopy for a wide range of nuclei in the region as well as experimental\ndata on Gamow-Teller strength distributions. We discuss the systematics of the\ndistributions and their centroids. We also predict the strength distributions\nfor several nuclei involving stable isotopes that should be experimentally\naccessible for one-particle exchange reactions in the near future.", "category": "nucl-th" }, { "text": "Fully antisymmetrised dynamics for bulk fermion systems: The neutron star's crust and mantel are typical examples of non-uniform bulk\nsystems with spacial localisations. When modelling such systems at low\ntemperatures, as is the case in the crust, one has to work with antisymmetrised\nmany-body states to get the correct fermion behaviour. Fermionic molecular\ndynamics, which works with an antisymmetrised product of localised wave\npackets, should be an appropriate choice. Implementing periodic boundary\nconditions into the fermionic molecular dynamics formalism would allow the\nstudy of the neutron star's crust as a bulk quantum system. Unfortunately, the\nantisymmetrisation is a non-local entanglement which reaches far out of the\nperiodically repeated unit cell. In this proceeding, we give a brief overview\nhow periodic boundary conditions and fermionic molecular dynamics can be\ncombined without truncating the long-range many-body correlation induced by the\nantisymmetry of the many-body state.", "category": "nucl-th" }, { "text": "Dynamical Model for Meson Production off Nucleon and Application to\n Neutrino-Nucleus Reactions: I explain the Sato-Lee (SL) model and its extension to the neutrino-induced\npion production off the nucleon. Then I discuss applications of the SL model to\nincoherent and coherent pion productions in the neutrino-nucleus scattering. I\nmention a further extension of this approach with a dynamical coupled-channels\nmodel developed in Excited Baryon Analysis Center of JLab.", "category": "nucl-th" }, { "text": "Breakup Reactions of 11Li within a Three-Body Model: We use a three-body model to investigate breakup reactions of 11Li (n+n+9Li)\non a light target. The interaction parameters are constrained by known\nproperties of the two-body subsystems, the 11Li binding energy and\nfragmentation data. The remaining degrees of freedom are discussed. The\nprojectile-target interactions are described by phenomenological optical\npotentials. The model predicts dependence on beam energy and target,\ndifferences between longitudinal and transverse momentum distributions and\nprovides absolute values for all computed differential cross sections. We give\nan almost complete series of observables and compare with corresponding\nmeasurements. Remarkably good agreement is obtained. The relative neutron-9Li\np-wave content is about 40%. A p-resonance, consistent with measurements at\nabout 0.5 MeV of width about 0.4 MeV, seems to be necessary. The widths of the\nmomentum distributions are insensitive to target and beam energy with a\ntendency to increase towards lower energies. The transverse momentum\ndistributions are broader than the longitudinal due to the diffraction process.\nThe absolute values of the cross sections follow the neutron-target cross\nsections and increase strongly for beam energies decreasing below 100 MeV/u.", "category": "nucl-th" }, { "text": "Precise comparison of the Gaussian expansion method and the Gamow shell\n model: We perform a detailed comparison of results of the Gamow Shell Model (GSM)\nand the Gaussian Expansion Method (GEM) supplemented by the complex scaling\n(CS) method for the same translationally-invariant cluster-orbital shell model\n(COSM) Hamiltonian. As a benchmark test, we calculate the ground state $0^{+}$\nand the first excited state $2^{+}$ of mirror nuclei $^{6}$He and $^{6}$Be in\nthe model space consisting of two valence nucleons in $p$-shell outside of a\n$^{4}$He core. We find a good overall agreement of results obtained in these\ntwo different approaches, also for many-body resonances.", "category": "nucl-th" }, { "text": "The nucleon resonances in the $J/\u03c8\\to p\\bar{p}\u03b7'$ decay: We are aiming to study the $J/\\psi \\to p\\bar{p}\\eta'$ decay in an isobar\nmodel and the effective Lagrangian approach. After a careful exploration of the\ncontributions of the $S_{11}(1535)$, $P_{11}(1710)$, $P_{13}(1900)$,\n$S_{11}(2090)$ and $P_{11}(2100)$ resonances, we conclude that either a\nsubthreshold resonance or a broad $P$-wave state in the near threshold range\nseems to be indispensable to describe present data of the $\\pi N \\to \\eta'N$.\nFurthermore, at least one broad resonance above $\\eta'N$ threshold is\npreferred. With this detailed analysis, we could give the invariant mass\nspectrum and Dalitz plot of the $J/\\psi \\to p\\bar{p}\\eta'$ decay for the\npurpose of assisting the future detailed partial wave analysis. It is found\nthat the $J/\\psi \\to p\\bar{p}\\eta'$ data are useful for disentangling the above\nor below threshold resonant contribution, though it still further needs the\ndifferential cross section data of $\\pi N \\to \\eta'N$ to realize some of the\nresonant and the non-resonant contribution. Our results are enlightening for\nthe $\\eta'N$ production mechanism and the properties of the nucleon resonances\nwith the mass around 2.0~GeV.", "category": "nucl-th" }, { "text": "Transfer/Breakup Channel Couplings in Sub-barrier Fusion Reactions: With the recent availability of state-of-the-art radioactive ion beams, there\nhas been a renew interest in the investigation of nuclear reactions with heavy\nions near the Coulomb barrier. The role of inelastic and transfer channel\ncouplings in fusion reactions induced by stable heavy ions can be revisited.\nDetailed Analysis of recent experimental fusion cross sections by using\nstandard coupled-channel calculations is first discussed. Multi-neutron\ntransfer effects are introduced in the fusion process below the Coulomb barrier\nby analyzing 32S+90,96Zr as benchmark reactions. The enhancement of fusion\ncross sections for 32S+96Zr is well reproduced at sub-barrier energies by NTFus\ncode calculations including the coupling of the neutron-transfer channels\nfollowing the Zagrebaev semi-classical model. Similar effects for 40Ca+90Zr and\n40Ca+96Zr fusion excitation functions are found. The breakup coupling in both\nthe elastic scattering and in the fusion process induced by weakly bound stable\nprojectiles is also shown to be crucial. In the second part of this work, full\ncoupled-channel calculations of the fusion excitation functions are performed\nby using the breakup coupling for the more neutron-rich reaction and for the\nmore weakly bound projectiles. we clearly demonstrate that\nContinuum-Discretized Coupled-Channel calculations are capable to reproduce the\nfusion enhancement from the breakup coupling in 6Li+59Co.", "category": "nucl-th" }, { "text": "Generic Constraints on the Relativistic Mean-Field and\n Skyrme-Hartree-Fock Models from the Pure Neutron Matter Equation of State: We study the nuclear symmetry energy S(rho) and related quantities of nuclear\nphysics and nuclear astrophysics predicted generically by relativistic\nmean-field (RMF) and Skyrme-Hartree-Fock (SHF) models. We establish a simple\nprescription for preparing equivalent RMF and SHF parametrizations starting\nfrom a minimal set of empirical constraints on symmetric nuclear matter,\nnuclear binding energy and charge radii, enforcing equivalence of their Lorenz\neffective masses, and then using the pure neutron matter (PNM) equation of\nstate (EoS) obtained from ab-initio calculations to optimize the pure isovector\nparameters in the RMF and SHF models. We find the resulting RMF and SHF\nparametrizations give broadly consistent predictions of the symmetry energy J\nand its slope parameter L at saturation density within a tight range of <~2 MeV\nand <~6 MeV respectively, but that clear model dependence shows up in the\npredictions of higher-order symmetry energy parameters, leading to important\ndifferences in (a) the slope of the correlation between J and L from the\nconfidence ellipse, (b) the isospin-dependent part of the incompressibility of\nnuclear matter K_tau, (c) the symmetry energy at supra-saturation densities,\nand (d) the predicted neutron star radii. The model dependence can lead to\nabout 1-2 km difference in predictions of the neutron star radius given\nidentical predicted values of J, L and symmetric nuclear matter (SNM)\nsaturation properties. Allowing the full freedom in the effective masses in\nboth models leads to constraints of 30<~J<~31.5 MeV, 35<~L<~60 MeV,\n-330<~K_tau<~-216 MeV for the RMF model as a whole and 30<~J<~33 MeV, 28<~L<~65\nMeV, -420<~K_tau<~-325 MeV for the SHF model as a whole. Notably, given PNM\nconstraints, these results place RMF and SHF models as a whole at odds with\nsome constraints on K_tau inferred from giant monopole resonance and neutron\nskin experimental results.", "category": "nucl-th" }, { "text": "Removal of $K$-mixing in angular momentum projected nuclear wave\n functions: Angular momentum projection plays a key role in studying nuclei and other\nquantum many-body systems with rotational invariance. In this Letter, we report\na new fundamental feature of the angular momentum projection, which clearly\ntells us the frequently discussed $K$-mixing in the angular momentum projected\nnuclear wave function can be safely removed. At a given spin $J$, one can\ngenerate $2J+1$ angular momentum projected states from a deformed Slater\ndeterminant. These projected states are labeled with different $K$ numbers.\nUsually, a nuclear wave function with $K$-mixing can be expressed as an\nexpansion in terms of all these $2J+1$ projected states. The coefficients in\nthis expansion can be obtained by solving the Hill-Wheeler equation.\nStrikingly, we found that such nuclear wave function with $K$-mixing can always\nbe equivalently replaced by a single projected state generated from another\nSlater determinant. Consequently, such nuclear wave function can be\nsignificantly simplified, especially for high-spin states. This also reminds us\nthat the $K$-mixing in the angular momentum projected nuclear wave functions,\nadopted by many present-day nuclear models, does not carry any physical\nmeaning, and is essentially different from that $K$-mixing caused by the\nCoriolis force in the cranked shell model.", "category": "nucl-th" }, { "text": "Short History of Nuclear Many-Body Problem: This is a very short presentation regarding developments in the theory of\nnuclear many-body problems, as seen and experienced by the author during the\npast 60 years with particular emphasis on the contributions of Gerry Brown and\nhis research-group. Much of his work was based on Brueckner's formulation of\nthe nuclear many-body problem. It is reviewed briefly together with the\nMoszkowski-Scott separation method that was an important part of his early\nwork. The core-polarisation and his work related to effective interactions in\ngeneral are also addressed.", "category": "nucl-th" }, { "text": "Nuclear response for the Skyrme effective interaction with zero-range\n tensor terms. II. Sum rules and instabilities: The formalism of linear response theory for Skyrme forces including tensor\nterms presented in article [1] is generalized for the case of a Skyrme energy\ndensity functional in infinite matter. We also present analytical results for\nthe odd-power sum rules, with particular attention to the inverse energy\nweighted sum rule, $M_{-1}$, as a tool to detect instabilities in Skyrme\nfunctionals.", "category": "nucl-th" }, { "text": "Proto-Strange Quark Star Structure: In this paper, we investigate the newborn strange quark stars with constant\nentropy. We also use the MIT bag model to calculate the thermodynamic\nproperties in two cases; the density-dependent bag constant and the fixed bag\nconstant (B = 90 MeV). We show that the equation of state becomes stiffer by\nusing the density dependent bag constant and by increasing the entropy.\nFurthermore, we show that the adiabatic index of the system reaches to 4/3 at\nhigh densities. Later, we calculate the structure of a strange quark star using\nthe equation of state and the general relativistic equations of hydrostatic\nequilibrium, the Tolman-Oppenheimer-Volkoff (TOV) equations. We show that the\ngravitational mass of the star decreases by increasing the entropy and the\nmaximum gravitational mass is larger when we use the density-dependent bag\nconstant at fixed central energy density. It is shown that the mass-radius\nrelation for this system obeys M R^ 3 for different cases of the calculations.\nFinally, we show that for a given stellar mass considering the fixed bag\nconstant, the maximum gravitational red shift of a strange quark star occurs at\nlarger values of entropy.", "category": "nucl-th" }, { "text": "Daejeon16 NN Interaction: We have developed a realistic nucleon-nucleon (NN) interaction, dubbed\nDaejeon16. We start from a SRG (similarity renormalization group) evolved\nchiral N3LO interaction. We then apply PETs (phase-equivalent transformations)\nto the SRG-evolved interaction. It turned out that the obtained in such a way\nDaejeon16 NN interaction provides a good description of various observables in\nlight nuclei without NNN forces. In this contribution, we present our new\nresults for some selected nuclei using the ab initio no-core shell model (NCSM)\nwith the Daejeon16 interaction. One of the interesting results is that the ab\ninitio NCSM with Daejeon16 clearly demonstrates the phenomenon of parity\ninversion in Be-11, i.e., the ground state in Be-11 has the spin-parity (1/2,\n+) in experiments contrary to the expectation from the conventional shell model", "category": "nucl-th" }, { "text": "Heavy Ion Dynamics and Neutron Stars: Some considerations are reported, freely inspired from the presentations and\ndiscussions during the Beijing Normal University Workshop on the above Subject,\nheld in July 2007. Of course this cannot be a complete summary but just a\ncollection of personal thougths aroused during the meeting.", "category": "nucl-th" }, { "text": "Surface effects in color superconducting strange-quark matter: Surface effects in strange-quark matter play an important role for certain\nobservables which have been proposed in order to identify strange stars, and\ncolor superconductivity can strongly modify these effects. We study the surface\nof color superconducting strange-quark matter by solving the\nHartree-Fock-Bogoliubov equations for finite systems (\"strangelets\") within the\nMIT bag model, supplemented with a pairing interaction. Due to the bag-model\nboundary condition, the strange-quark density is suppressed at the surface.\nThis leads to a positive surface charge, concentrated in a layer of ~1 fm below\nthe surface, even in the color-flavor locked (CFL) phase. However, since in the\nCFL phase all quarks are paired, this positive charge is compensated by a\nnegative charge, which turns out to be situated in a layer of a few tens of fm\nbelow the surface, and the total charge of CFL strangelets is zero. We also\nstudy the surface and curvature contributions to the total energy. Due to the\nstrong pairing, the energy as a function of the mass number is very well\nreproduced by a liquid-drop type formula with curvature term.", "category": "nucl-th" }, { "text": "Isospin-symmetry breaking in superallowed Fermi beta-decay due to\n isospin-nonconserving forces: We investigate isospin-symmetry breaking effects in the sd-shell region with\nlarge-scale shell-model calculations, aiming to understand the recent anomalies\nobserved in superallowed Fermi beta-decay. We begin with calculations of\nCoulomb displacement energies (CDE's) and triplet displacement energies (TDE's)\nby adding the T=1,J=0 isospin nonconserving (INC) interaction into the usual\nisospin-invariant Hamiltonian. It is found that CDE's and TDE's can be\nsystematically described with high accuracy. A total number of 122 one- and\ntwo-proton separation energies are predicted accordingly, and locations of the\nproton drip-line and candidates for proton-emitters are thereby suggested.\nHowever, attempt to explain the anomalies in the superallowed Fermi beta-decay\nfails because these well-fitted T=1,J=0 INC interactions are found no effects\non the nuclear matrix elements. It is demonstrated that the observed large\nisospin-breaking correction in the 32Cl beta-decay, the large isospin-mixing in\nthe 31Cl beta-decay, and the small isospin-mixing in the 23Al beta-decay can be\nconsistently understood by introducing additional T=1,J=2 INC interactions\nrelated to the s1/2 orbit.", "category": "nucl-th" }, { "text": "Microscopic analysis of quasielastic scattering and breakup reactions of\n neutron-rich nuclei $^{12,14}$Be: A microscopic analysis of the optical potentials (OPs) and cross sections of\nquasielastic scattering of $^{12,14}$Be on $^{12}$C at 56 MeV/nucleon and on\nprotons at energy near 700 MeV is carried out. For lower energy scattering the\nreal part of the OP is calculated by using of double-folding procedure\naccounting for the anti-symmetrization effects, while the imaginary part is\nobtained on the base of the high-energy approximation (HEA). The HEA is also\napplied to the calculations of both real and imaginary OPs when solving the\nrelativistic equation for the high-energy proton-nucleus elastic scattering.\nThe neutron and proton density distributions computed in different microscopic\nmodels for $^{12}$Be and $^{14}$Be are used. In the present hybrid model of the\noptical potential the only free parameters are the depths of the real and\nimaginary parts of OP obtained by fitting the experimental data. The role of\nthe inelastic scattering channel to the first excited $2^{+}$ and $3^{-}$\nstates in $^{12}$C when calculating the quasielastic cross sections, as well as\nthe modified density of the $^{12}$C target accounting for the surface effects\nare studied. In addition, the cluster model, in which $^{14}$Be consists of a\n$2n$-halo and the $^{12}$Be core, is applied to calculate the cross sections of\ndiffraction breakup and stripping reactions in $^{14}$Be+$^{12}$C scattering\nand longitudinal momentum distributions of $^{12}$Be fragments at energy of 56\nMeV/nucleon. A good agreement of the theoretical results with the available\nexperimental data of both quasielstic scattering and breakup processes is\nobtained.", "category": "nucl-th" }, { "text": "Nuclear deformation in the laboratory frame: We develop a formalism for calculating the distribution of the axial\nquadrupole operator in the laboratory frame within the rotationally invariant\nframework of the configuration-interaction shell model. The calculation is\ncarried out using a finite-temperature auxiliary-field quantum Monte Carlo\nmethod. We apply this formalism to isotope chains of even-mass samarium and\nneodymium nuclei, and show that the quadrupole distribution provides a\nmodel-independent signature of nuclear deformation. Two technical advances are\ndescribed that greatly facilitate the calculations. The first is to exploit the\nrotational invariance of the underlying Hamiltonian to reduce the statistical\nfluctuations in the Monte Carlo calculations. The second is to determine\nquadruple invariants from the distribution of the axial quadrupole operator.\nThis allows us to extract effective values of the intrinsic quadrupole shape\nparameters without invoking an intrinsic frame or a mean-field approximation.", "category": "nucl-th" }, { "text": "The role of the likelihood for elastic scattering uncertainty\n quantification: Background: Analyses of elastic scattering with the optical model (OMP) are\nwidely used in nuclear reactions.\n Purpose: Previous work compared a traditional frequentist approach and a\nBayesian approach to quantify uncertainties in the OMP. In this study, we\nrevisit this comparison and consider the role of the likelihood used in the\nanalysis.\n Method: We compare the Levenberg-Marquardt algorithm for $\\chi^{2}$\nminimization with Markov Chain Monte Carlo sampling to obtain parameter\nposteriors. Following previous work, we consider how results are affected when\n$\\chi^{2}$/N is used for the likelihood function, N being the number of data\npoints, to account for possible correlations in the model and underestimation\nof the error in the data.\n Results: We analyze a simple linear model and then move to OMP analysis of\nelastic angular distributions using a) a 5-parameter model and b) a 6-parameter\nmodel. In the linear model, the frequentist and Bayesian approaches yield\nconsistent optima and uncertainty estimates. The same is qualitatively true for\nthe 5-parameter OMP analysis. For the 6-parameter OMP analysis, the parameter\nposterior is no longer well-approximated by a Gaussian and a covariance-based\nfrequentist prediction becomes unreliable. In all cases, when the Bayesian\napproach uses $\\chi^{2}$/N in the likelihood, uncertainties increase by\n$\\sqrt{N}$.\n Conclusions: When the parameter posterior is near-Gaussian and the same\nlikelihood is used, the frequentist and Bayesian approaches recover consistent\nparameter uncertainty estimates. If the parameter posterior has significant\nhigher moments, the covariance-only frequentist approach becomes unreliable and\nthe Bayesian approach should be used. Empirical coverage can serve as an\nimportant internal check for uncertainty estimation, providing red flags for\nuncertainty analyses.", "category": "nucl-th" }, { "text": "A hydrodynamic study of hyperon spin polarization in relativistic heavy\n ion collisions: We perform a systematic study of the spin polarization of hyperons in\nheavy-ion collisions using the MUSIC hydrodynamic model with A Multi-Phase\nTransport (AMPT) pre-equilibrium dynamics. Our model calculations nicely\ndescribe the measured collision-energy, centrality, rapidity, and $p_T$\ndependence of $\\Lambda$ polarization. We also study and predict the global spin\npolarization of $\\Xi^-$ and $\\Omega^-$ as a function of collision energy, which\nprovides a baseline for the studies of the magnetic moment, spin, and mass\ndependence of the spin polarization. For the local spin polarization, we\ncalculate the radial and azimuthal components of the transverse $\\Lambda$\npolarization and find specific modulating behavior which could reflect the\ncircular vortical structure. However, our model fails to describe the\nazimuthal-angle dependence of the longitudinal and transverse $\\Lambda$\npolarization, which indicates that the hydrodynamic framework with the spin\nCooper-Frye formula under the assumption of thermal equilibrium of spin degree\nof freedom needs to be improved.", "category": "nucl-th" }, { "text": "Effects of momentum conservation on the analysis of anisotropic flow: We present a general method for taking into account correlations due to\nmomentum conservation in the analysis of anisotropic flow, either by using the\ntwo-particle correlation method or the standard flow vector method. In the\nlatter, the correlation between the particle and the flow vector is either\ncorrected through a redefinition (shift) of the flow vector, or subtracted\nexplicitly from the observed flow coefficient. In addition, momentum\nconservation contributes to the reaction plane resolution. Momentum\nconservation mostly affects the first harmonic in azimuthal distributions,\ni.e., directed flow. It also modifies higher harmonics, for instance elliptic\nflow, when they are measured with respect to a first harmonic event plane such\nas one determined with the standard transverse momentum method. Our method is\nillustrated by application to NA49 data on pion directed flow.", "category": "nucl-th" }, { "text": "Stable Bose-Einstein correlations: The shape of Bose-Einstein (or HBT) correlation functions is determined for\nthe case when particles are emitted from a stable source, obtained after\nconvolutions of large number of elementary random processes. The two-particle\ncorrelation function is shown to have a {\\it stretched exponential} shape,\ncharacterized by the L\\'evy index of stability $ 0 < \\alpha \\le 2$ and the\nscale parameter $R$. The normal, Gaussian shape corresponds to a particular\ncase, when $\\alpha = 2$ is selected. The asymmetry parameter of the stable\nsource, $\\beta$ is shown to be proportional to the angle, measured by the\nnormalized three-particle cumulant correlations.", "category": "nucl-th" }, { "text": "Open charm in nuclear matter at finite temperature: We study the properties of open-charm mesons ($D$ and $\\bar {D}$) in nuclear\nmatter at finite temperature within a self-consistent coupled-channel approach.\nThe meson-baryon interactions are adopted from a type of broken SU(4) s-wave\nTomozawa-Weinberg terms supplemented by an attractive scalar-isoscalar\nattraction. The in-medium solution at finite temperature incorporates Pauli\nblocking effects, mean-field binding on all the baryons involved, and $\\pi$ and\nopen-charm meson self-energies in a self-consistent manner. In the $DN$ sector,\nthe $\\Lambda_c$ and $\\Sigma_c$ resonances, generated dynamically at 2593 MeV\nand 2770 MeV in free space, remain close to their free-space position while\nacquiring a remarkable width due to the thermal smearing of Pauli blocking as\nwell as from the nuclear matter density effects. As a result, the $D$ meson\nspectral density shows a single pronounced peak for energies close to the $D$\nmeson free-space mass that broadens with increasing matter density with an\nextended tail particularly towards lower energies. The $\\bar D$ potential shows\na moderate repulsive behavior coming from the dominant I=1 contribution of the\n$\\bar D N$ interaction. The low-density theorem is, however, not a good\napproximation for the $\\bar D$ self-energy in spite of the absence of\nresonance-hole contributions close to threshold in this case. We speculate the\npossibility of $D$-mesic nuclei as well as discuss some consequences for the\n$J/\\Psi$ suppression in heavy-ion collisions, in particular for the future CBM\nexperiment at FAIR.", "category": "nucl-th" }, { "text": "Continuum and three-nucleon force in Borromean system: The 17Ne case: Starting from chiral two-nucleon (2NF) and chiral three-nucleon (3NF)\npotentials, we present a detailed study of 17Ne, a Borromean system, with the\nGamow shell model which can capture continuum effects. More precisely, we take\nadvantage of the normal-ordering approach to include the 3NF and the Berggren\nrepresentation to treat bound, resonant and continuum states on equal footing\nin a complex-momentum plane. In our framework, 3NF is essential to reproduce\nthe Borromean structure of 17Ne, while the continuum is more crucial for the\nhalo property of the nucleus. The two-proton halo structure is demonstrated by\ncalculating the valence proton density and correlation density. The\nastrophysically interesting $3/2^-$ excited state has its energy above the\nthreshold of the proton emission, and therefore the two-proton decay should be\nexpected from the state.", "category": "nucl-th" }, { "text": "Local nucleon-nucleon and three-nucleon interactions within chiral\n effective field theory: To obtain an understanding of the structure and reactions of nuclear systems\nfrom first principles has been a long-standing goal of nuclear physics. In this\nrespect, few- and many-body systems provide a unique laboratory for studying\nnuclear interactions. During the past decades, the development of accurate\nrepresentations of the nuclear force has undergone substantial progress.\nParticular emphasis has been devoted to chiral effective field theory (EFT), a\nlow-energy effective representation of quantum chromodynamics (QCD). Within\nchiral EFT, many studies have been carried out dealing with the construction of\nboth the nucleon-nucleon ($N\\!N$) and three-nucleon ($3N$) interactions. The\naim of the present article is to give a detailed overview of the chiral\ninteraction models that are local in configuration space, and show recent\nresults for nuclear systems obtained by employing these local chiral forces.", "category": "nucl-th" }, { "text": "Deformation effects in the Coulomb breakup of 31Ne: We present a fully quantum mechanical theory to study the effects of\ndeformation on various reaction observables in the Coulomb breakup of neutron\nrich exotic medium mass nuclei on heavy targets within the framework of finite\nrange distorted wave Born approximation by using a deformed Woods-Saxon\npotential. As an application of this theory, we calculate the one-neutron\nremoval cross section, relative energy spectra, parallel momentum distributions\nand angular distributions in the breakup of 31Ne on Pb and Au targets at 234\nMeV/u. We suggest ways to put constraints on the large uncertainty in the\none-neutron separation energy of 31Ne and also argue that if 31Ne is indeed a\nhalo nucleus then it should be a deformed one.", "category": "nucl-th" }, { "text": "Nuclear matter with three-body forces from self-consistent spectral\n calculations: We calculate the equation of state of nuclear matter in the self-consistent\nT-matrix scheme including three-body nuclear interactions. We study the effect\nof the three-body force on the self-energies and spectral functions of nucleons\nin medium.", "category": "nucl-th" }, { "text": "Towards a New Strategy of Searching for QCD Phase Transition in Heavy\n Ion Collisions: We reconsider the Hung and Shuryak arguments in favour of searching for the\ndeconfinement phase transition in heavy ion collisions {\\em downward} from the\nnominal SPS energy, at $E_{lab} \\approx 30 \\ GeV/A$ where the fireball lifetime\nis the longest one. Using the recent lattice QCD data and the mixed phase\nmodel, we show that the deconfinement transition might occur at the bombarding\nenergies as low as $E_{lab}=3 - 5 \\ GeV/A$. Attention is drawn to the study of\nthe mixed phase of nuclear matter in the collision energy range $E_{lab}= 2-10\n\\ GeV/A$.", "category": "nucl-th" }, { "text": "Wavelet Methods in the Relativistic Three-Body Problem: In this paper we discuss the use of wavelet bases to solve the relativistic\nthree-body problem. Wavelet bases can be used to transform momentum-space\nscattering integral equations into an approximate system of linear equations\nwith a sparse matrix. This has the potential to reduce the size of realistic\nthree-body calculations with minimal loss of accuracy. The wavelet method leads\nto a clean, interaction independent treatment of the scattering singularities\nwhich does not require any subtractions.", "category": "nucl-th" }, { "text": "The $S_{E1}$ factor of radiative $\u03b1$ capture on $^{12}$C in\n effective field theory: The $S_{E1}$ factor of radiative $\\alpha$ capture on $^{12}$C is studied in\neffective field theory. We briefly discuss the strategy for the calculation of\nthe reaction and report a first result of $S_{E1}$ at the Gamow-peak energy,\n$E_G=0.3$~MeV.", "category": "nucl-th" }, { "text": "Bayesian inference of neutron-star observables based on effective\n nuclear interactions: Based on the Skyrme-Hartree-Fock model (SHF) as well as its extension (the\nKorea-IBS-Daegu-SKKU (KIDS) model) and the relativistic mean-field (RMF) model,\nwe have studied the constraints on the parameters of the nuclear matter\nequation of state (EOS) from adopted astrophysical observables using a Bayesian\napproach. While the masses and radii of neutron stars generally favors a stiff\nisoscalar EOS and a moderately soft nuclear symmetry energy, model dependence\non the constraints is observed and mostly originates from the incorporation of\nhigher-order EOS parameters and difference between relativistic and\nnon-relativistic models. At twice saturation density, the value of the symmetry\nenergy is constrained to be $48^{+15}_{-11}$ MeV in the standard SHF model,\n$48^{+8}_{-15}$ MeV in the KIDS model, and $48^{+5}_{-6}$ MeV in the RMF model,\naround their maximum {\\it a posteriori} values within $68\\%$ confidence\nintervals. Our study helps to obtain a robust constraint on nuclear matter EOS,\nand meanwhile, to understand the model dependence of the results.", "category": "nucl-th" }, { "text": "Coupled fermion and boson production in a strong background mean-field: We derive quantum kinetic equations for fermion and boson production starting\nfrom a phi^4 Lagrangian with minimal coupling to fermions. Decomposing the\nscalar field into a mean-field part and fluctuations we obtain spontaneous pair\ncreation driven by a self-interacting strong background field. The produced\nfermion and boson pairs are self-consistently coupled. Consequently back\nreactions arise from fermion and boson currents determining the time dependent\nself-interacting background mean-field. We explore the numerical solution in\nflux tube geometry for the time evolution of the mean-field as well as for the\nnumber- and energy densities for fermions and bosons. We find that after a\ncharacteristic time all energy is converted from the background mean-field to\nparticle creation. Applying this general approach to the production of\n``quarks'' and ``gluons'' a typical time scale for the collapse of the flux\ntube is 1.5 fm/c.", "category": "nucl-th" }, { "text": "First Order Variational Calculation of Form Factor in a Scalar\n Nucleon--Meson Theory: We investigate a relativistic quantum field theory in the particle\nrepresentation using a non-perturbative variational technique. The theory is\nthat of two massive scalar particles, `nucleons' and `mesons', interacting via\na Yukawa coupling. We calculate the general Euclidean Green function involving\ntwo external nucleons and an arbitrary number of external mesons in the\nquenched approximation for the nucleons. The non-perturbative renormalization\nand truncation is done in a consistent manner and results in the same\nvariational functional independent of the number of external mesons. We check\nthat the calculation agrees with one-loop perturbation theory for small\ncouplings. As an illustration the special case of meson absorption on the\nnucleon is considered in detail. We derive the radius of the dressed particle\nand numerically investigate the vertex function after analytic continuation to\nMinkowski space.", "category": "nucl-th" }, { "text": "Porter-Thomas distribution in unstable many-body systems: We use the continuum shell model approach to explore the resonance width\ndistribution in unstable many-body systems. The single-particle nature of a\ndecay, the few-body character of the interaction Hamiltonian, and collectivity\nthat emerges in non-stationary systems due to the coupling to the continuum of\nreaction states are discussed. Correlations between structures of the parent\nand daughter nuclear systems in the common Fock space are found to result in\ndeviations of decay width statistics from the Porter-Thomas distribution.", "category": "nucl-th" }, { "text": "Equilibration and locality: Experiments motivated by predictions of quantum mechanics indicate\nnon-trivial correlations between spacelike-separated measurements. The\nphenomenon is referred to as a violation of strong-locality and, after\nEinstein, called ghostly action at a distance. An intriguing and previously\nunasked question is how the evolution of an assembly of particles to\nequilibrium-state relates to strong-locality. More specifically, whether, with\nthis respect, indistinguishable particles differ from distinguishable ones.\n To address the question, we introduce a Markov-chain based framework over a\nfinite set of microstates. For the first time, we formulate conditions needed\nto obey the particle transport- and strong-locality for indistinguishable\nparticles.\n Models which obey transport-locality and lead to equilibrium-state are\nconsidered. We show that it is possible to construct models obeying and\nviolating strong-locality both for indistinguishable particles and for\ndistinguishable ones. However, we find that only for distinguishable particles\nstrongly-local evolution to equilibrium is possible without breaking the\nmicrostate-symmetry. This is the strongest symmetry one can impose and leads to\nthe shortest equilibration time.\n We hope that the results presented here may provide a new perspective on a\nviolation of strong-locality, and the developed framework will help in future\nstudies. Specifically they may help to interpret results on high-energy nuclear\ncollisions indicating a fast equilibration of indistinguishable particles.", "category": "nucl-th" }, { "text": "Effect of short- and long-range correlations on neutron skins of various\n neutron-rich doubly magic nuclei: We study the effects of correlations beyond the independent particle model in\nthe evaluation of neutron skins of various neutron-rich doubly magic nuclei. We\nconsider short- and long-range correlations to take into account the presence\nof the strongly repulsive core of the bare nucleon-nucleon interaction and\ncollective nuclear phenomena, respectively. Despite the strong sensitivity on\nthe structure of the nucleus considered, our results indicate that, in general,\ncorrelations increase the values of the neutron skins.", "category": "nucl-th" }, { "text": "Parametric estimate of the relative photon yields from the Glasma and\n the Quark-Gluon Plasma in heavy-ion collisions: Recent classical-statistical numerical simulations have established the\n\"bottom-up\" thermalization scenario of Baier et al. as the correct weak\ncoupling effective theory for thermalization in ultrarelativistic heavy-ion\ncollisions. We perform a parametric study of photon production in the various\nstages of this bottom-up framework to ascertain the relative contribution of\nthe off-equilibrium \"Glasma\" relative to that of a thermalized Quark-Gluon\nPlasma. Taking into account the constraints imposed by the measured charged\nhadron multiplicities at RHIC and the LHC, we find that Glasma contributions\nare important especially for large values of the saturation scale at both\nenergies. These non-equilibrium effects should therefore be taken into account\nin studies where weak coupling methods are employed to compute photon yields.", "category": "nucl-th" }, { "text": "Observable Properties of Quark-Hadron Phase Transition at the Large\n Hadron Collider: Quark-hadron phase transition is simulated by an event generator that\nincorporates the dynamical properties of contraction due to QCD confinement\nforces and randomization due to the thermal behavior of a large quark system on\nthe edge of hadronization. Fluctuations of emitted pions in the $(\\eta,\\phi)$\nspace are analyzed using normalized factorial moments in a wide range of bin\nsizes. The scaling index $\\nu$ is found to be very close to the predicted value\nin the Ginzburg-Landau formalism. The erraticity indices $\\mu_q$ are determined\nin a number of ways that lead to the same consistent values. They are compared\nto the values from the Ising model, showing significant difference in a\ntransparent plot. Experimental determination of $\\nu$ and $\\mu_q$ at the LHC\nare now needed to check the reality of the theoretical study and to provide\nguidance for improving the model description of quark-hadron phase transition.", "category": "nucl-th" }, { "text": "Low-lying States of $^{6}$He and $^{6}$Be in Nodal Surface Structure\n Analysis: The low-lying states of light nuclei $^6$He and $^6$Be are studied. Using the\ninherent nodal surface(INS) analysis approach, we deduce the quantum numbers\nand the spatial symmetries of the low-lying states with positive parity and\nnegative parity of the two nuclei. The energy spectrum obtained agrees well\nwith the experimental data.", "category": "nucl-th" }, { "text": "Alpha Decay in the Complex Energy Shell Model: Alpha emission from a nucleus is a fundamental decay process in which the\nalpha particle formed inside the nucleus tunnels out through the potential\nbarrier. We describe alpha decay of $^{212}$Po and $^{104}$Te by means of the\nconfiguration interaction approach. To compute the preformation factor and\npenetrability, we use the complex-energy shell model with a separable T=1\ninteraction. The single-particle space is expanded in a Woods-Saxon basis that\nconsists of bound and unbound resonant states. Special attention is paid to the\ntreatment of the norm kernel appearing in the definition of the formation\namplitude that guarantees the normalization of the channel function. Without\nexplicitly considering the alpha-cluster component in the wave function of the\nparent nucleus, we reproduce the experimental alpha-decay width of $^{212}$Po\nand predict an upper limit of T_{1/2}=5.5x10^{-7} sec for the half-life of\n$^{104}$Te. The complex-energy shell model in a large valence configuration\nspace is capable of providing a microscopic description of the alpha decay of\nheavy nuclei having two valence protons and two valence neutrons outside the\ndoubly magic core. The inclusion of proton-neutron interaction between the\nvalence nucleons is likely to shorten the predicted half-live of $^{104}$Te.", "category": "nucl-th" }, { "text": "Effects of the equation of state on the bulk properties of\n maximally-rotating neutron stars: Neutron stars are among the densest known objects in the universe and an\nideal laboratory for the strange physics of super-condensed matter. While the\nsimultaneously measurements of mass and radius of non-rotating neutron stars\nmay impose constraints on the properties of the dense nuclear matter, the\nobservation and study of maximally-rotating ones, close to the mass-shedding\nlimit, may lead to significantly further constraints. Theoretical predictions\nallow neutron stars to rotate extremely fast (even more than $2000 \\ {\\rm\nHz}$). However, until this moment, the fastest observed rotating pulsar has a\nfrequency of $716 \\ {\\rm Hz}$, much lower compared to the theoretical\npredictions. There are many suggestions for the mechanism which lead to this\nsituation. In any case, the theoretical study of uniformly rotating neutron\nstars, along with the accurate measurements, may offer rich information\nconcerning the high density part of the equation of state. In addition, neutron\nstars through their evolution, may provide us with a criteria to determine the\nfinal fate of a rotating compact star. Sensitivity of bulk neutron stars\nproperties on the equation of state at the mass-shedding limit are the main\nsubject of the present study.", "category": "nucl-th" }, { "text": "Anisotropic flow in Cu+Au collisions at $\\sqrt{s_{NN}}=200$ GeV: The anisotropic flow of charged hadrons in asymmetric Cu+Au collisions at the\nRelativistic Heavy Ion Collider is studied in a multi-phase transport model.\nCompared with previous results for symmetric Au+Au collisions, charged hadrons\nproduced around midrapidity in asymmetric collisions are found to have a\nstronger directed flow $v_{1}$ and their elliptic flow $% v_{2} $ is also more\nsensitive to the parton scattering cross section. While higher-order flows\n$v_{3}$ and $v_{4}$ are small at all rapidities, both $% v_{1}$ and $v_{2}$ in\nthese collisions are appreciable and show an asymmetry in forward and backward\nrapidities.", "category": "nucl-th" }, { "text": "Nuclear viscosity estimated by dynamics of neck formation in the early\n stage of nuclear collision: The very early stage of the coalescence of two nuclei is studied and used to\nestimate the nuclear viscosity. The time evolution of the neck region has been\nsimulated by the unified Langevin equation method, which is used in the\nanalysis of heavy-ion collisions from the approaching stage to the\nfusion-fission stage. It is found that the transition from viscous to inertial\ncoalescence that appeared in the neck growth of macroscopic drops can also be\nseen in the present simulation in nucleus-nucleus collisions. The dynamics of\nneck growth is analyzed in terms of the hydrodynamical formula and the\nviscosity coefficient of nuclear matter is estimated using the analogy of\nmacroscopic drops.", "category": "nucl-th" }, { "text": "Hans Bethe: The Nuclear Many Body Problem: We discuss the work of Hans Bethe and others in formulating a theoretical\nfoundation for the nuclear shell model. Written for a general audience, this\narticle describes the evolution from Brueckner's reaction matrix theory to the\nMoszkowski-Scott separation method and ultimately to the Reference Spectrum\nmethod of Bethe, Brandow, and Petschek. We also discuss connections with the\nrecently developed low momentum nucleon-nucleon interactions.", "category": "nucl-th" }, { "text": "Center-of-mass effects on the quasi-hole spectroscopic factors in the\n 16O(e,e'p) reaction: The spectroscopic factors for the low-lying quasi-hole states observed in the\n16O(e,e'p)15N reaction are reinvestigated with a variational Monte Carlo\ncalculation for the structure of the initial and final nucleus. A computational\nerror in a previous report is rectified. It is shown that a proper treatment of\ncenter-of-mass motion does not lead to a reduction of the spectroscopic factor\nfor $p$-shell quasi-hole states, but rather to a 7% enhancement. This is in\nagreement with analytical results obtained in the harmonic oscillator model.\nThe center-of-mass effect worsens the discrepancy between present theoretical\nmodels and the experimentally observed single-particle strength. We discuss the\npresent status of this problem, including some other mechanisms that may be\nrelevant in this respect.", "category": "nucl-th" }, { "text": "Microscopic Structure of High-Spin Vibrational Excitations in\n Superdeformed 190,192,194Hg: Microscopic RPA calculations based on the cranked shell model are performed\nto investigate the quadrupole and octupole correlations for excited\nsuperdeformed bands in 190Hg, 192Hg, and 194Hg. The K=2 octupole vibrations are\npredicted to be the lowest excitation modes at zero rotational frequency. At\nfinite frequency, however, the interplay between rotation and vibrations\nproduces different effects depending on neutron number: The lowest octupole\nphonon is rotationally aligned in 190Hg, is crossed by the aligned\ntwo-quasiparticle bands in 192Hg, and retains the K=2 octupole vibrational\ncharacter up to the highest frequency in 194Hg. The gamma vibrations are\npredicted to be higher in energy and less collective than the octupole\nvibrations. From a comparison with the experimental dynamic moments of inertia,\na new interpretation of the observed excited bands invoking the K=2 octupole\nvibrations is proposed, which suggests those octupole vibrations may be\nprevalent in SD Hg nuclei.", "category": "nucl-th" }, { "text": "What can we learn from global spin alignment of $\u03c6$ meson in\n heavy-ion collisions?: We propose that a significant positive deviation from 1/3 for the spin\ndensity matrix element $\\rho_{00}$ of the $\\phi$ meson may indicate the\nexistence of a mean field of the $\\phi$ meson generated in heavy-ion\ncollisions. This explains why STAR preliminary data for the $\\phi$ meson's\n$\\rho_{00}$ are much larger than 1/3 while the data of $\\Lambda$ and\n$\\bar{\\Lambda}$ polarization seem not to allow such a significant and positive\ndeviation. The contribution may be from the polarization of the strange quark\nand antiquark through the $\\phi$ field, an effective mode of the gluon field in\nstrong interaction. We show that $\\rho_{00}$ for the $\\phi$ meson is a good\nanalyzer for fields even if they may strongly fluctuate in space-time.", "category": "nucl-th" }, { "text": "The Collective Excitation Spectra of $\u03c3, \u03c9$ and $\u03c0$ Mesons\n in Nuclear Matter: The recent progress on the study of the collective excitation in relativistic\nnuclear matter is reviewed. The collective excitation modes are derived by\nmeson propagators in nuclear matter. The mesons we study are $\\sigma, \\omega,\n\\gamma$ and $\\pi$ mesons. For pion, we derived not only the relativistic\nparticle - hole, delta - hole excitations but also antiparticle excitations,\nsuch as particle - antiparticle, antidelta - particle, delta - antiparticle\nexcitations. By calculating the dispersion relation and the spin - isospin\ndependent response function, the effects of all these excitation are studied.", "category": "nucl-th" }, { "text": "Continuum random-phase approximation for gamma transition between\n excited states in neutron-rich nuclei: A characteristic feature of collective and particle-hole excitations in\nneutron-rich nuclei is that many of them couple to unbound neutron in continuum\nsingle-particle orbits. The continuum random phase approximation (cRPA) is a\npowerful many-body method that describes such excitations, and it provides a\nscheme to evaluate transition strengths from the ground state. In an attempt to\napply cRPA to the radiative neutron capture reaction, we formulate in the\npresent study an extended scheme of cRPA that describes gamma-transitions from\nthe excited states under consideration, which decay to low-lying excited states\nas well as the ground state. This is achieved by introducing a non-local\none-body operator which causes transitions to a low-lying excited state, and\ndescribing a density-matrix response against this operator. As a demonstration\nof this new scheme, we perform numerical calculation for dipole, quadrupole,\nand octupole excitations in $^{140}$Sn, and discuss E1 and E2 transitions\ndecaying to low-lying $2^{+}_{1,2}$ and $3^{-}_{1}$ states. The results point\nto cases where the branching ratio to the low-lying states is larger than or\ncomparable with that to the ground state. We discuss key roles of collectivity\nand continuum orbits in both initial and final states.", "category": "nucl-th" }, { "text": "Uncertainties in the eta-Nucleon Scattering Length and Effective Range: The coupled eta-N, pi-N, gamma-N system is described by a K-matrix method.\nThe parameters in this model are adjusted to get an optimal fit to pi-N --->pi-\nN$, pi-N --->eta-N$, gamma-N--->pi-N and gamma-N --->eta-N data in an energy\nrange of about 100MeV or so each side of the eta threshold. The outcome is the\nappearance of two solutions one which has an eta-nucleon scattering length (a)\nof about 1.0 fm and a second with a~0.2fm. However, the second solution has an\nunconventional non-Lorentian form for the T-matrix in the region of the\n1535(20)MeV and 1650(30)MeV S-wave pi-N resonances.", "category": "nucl-th" }, { "text": "Quark-hadron duality and the nuclear EMC effect: Recent data on polarized proton knockout reactions off He-4 nuclei suggest a\nsmall but nonzero modification of proton electromagnetic form factors in\nmedium. Using model independent relations derived on the basis of quark-hadron\nduality, we relate the medium modification of the form factors to the\nmodification at large x of the deep-inelastic structure function of a bound\nproton. This places strong constraints on models of the nuclear EMC effect\nwhich assume a large deformation of the intrinsic structure of the nucleon in\nmedium.", "category": "nucl-th" }, { "text": "Conservation laws in the $1f_{7/2}$ shell model of $^{48}$Cr: Conservation laws in the $1f_{7/2}$ shell model of $^{48}$Cr found in numeric\nstudies by Escuderos, Zamick and Bayman [A. Escuderos, L. Zamick, and B. F.\nBayman, arXiv:0506050 (2005)] and me [K. Neerg\\aa rd, Phys. Rev. C \\textbf{90},\n014318 (2014)] are explained by symmetry under particle-hole conjugation and\nthe structure of the irreps of the symplectic group Sp(4). A generalization is\ndiscussed.", "category": "nucl-th" }, { "text": "Uncertainty-quantified phenomenological optical potentials for\n single-nucleon scattering: Optical-model potentials (OMPs) continue to play a key role in nuclear\nreaction calculations. However, the uncertainty of phenomenological OMPs in\nwidespread use -- inherent to any parametric model trained on data -- has not\nbeen fully characterized, and its impact on downstream users of OMPs remains\nunclear. Here we assign well-calibrated uncertainties for two representative\nglobal OMPs, those of Koning-Delaroche and Chapel Hill '89, using Markov-Chain\nMonte Carlo for parameter inference. By comparing the canonical versions of\nthese OMPs against the experimental data originally used to constrain them, we\nshow how a lack of outlier rejection and a systematic underestimation of\nexperimental uncertainties contributes to bias of, and overconfidence in,\nbest-fit parameter values. Our updated, uncertainty-quantified versions of\nthese OMPs address these issues and yield complete covariance information for\npotential parameters. Scattering predictions generated from our ensembles show\nimproved performance both against the original training corpora of experimental\ndata and against a new \"test\" corpus comprising many of the experimental\nsingle-nucleon scattering data collected over the last twenty years. Finally,\nwe apply our uncertainty-quantified OMPs to two case studies of\napplication-relevant cross sections. We conclude that, for many common\napplications of OMPs, including OMP uncertainty should become standard\npractice. To facilitate their immediate use, digital versions of our updated\nOMPs and related tools for forward uncertainty propagation are included as\nSupplementary Material.", "category": "nucl-th" }, { "text": "Shape/Phase Transitions and Critical Point Symmetries in Atomic Nuclei: Shape/phase transitions in atomic nuclei have first been discovered in the\nframework of the Interacting Boson Approximation (IBA) model. Critical point\nsymmetries appropriate for nuclei at the transition points have been introduced\nas special solutions of the Bohr Hamiltonian, stirring the introduction of\nadditional new solutions describing wide ranges of nuclei. A short review of\nthese recent developments will be attempted.", "category": "nucl-th" }, { "text": "Rescattering of Vector Meson Daughters in High Energy Heavy Ion\n Collisions: We consider the role of hadronic rescattering of daughter kaons on the\nobserved mass spectra from $\\phi$ meson decays in ultra-relativistic heavy ion\ncollisions. A hadronic cascade code (RQMD v2.4) shows that $\\sim$26% of all\n$\\phi$'s decaying to $K^+K^-$ in central Pb+Pb collisions at SPS energies\n($E_{beam} = 158 GeV/A$) have a rescattered or absorbed daughter. This\nsignificantly affects the reconstructed invariant mass of the pair and shifts\n$\\phi$ mesons out of the mass peak. Kaon rescattering depletes the low velocity\nregion, hardening and broadening the observed phi $m_t$ and rapidity\ndistributions respectively, relative to the dilepton channel. This effect\nproduces an apparent change in the experimentally determined branching ratio\nnot necessarily related to chiral symmetry restoration. Comparisons to recent\nexperimental measures at CERN energies reveal a possible mechanism to account\nfor the shape of the observed spectra, though not their absolute relative\nmagnitude.", "category": "nucl-th" }, { "text": "Causal dissipative hydrodynamics obtained from the\n nonextensive/dissipative correspondence: We derive the constitutive equations of causal relativistic dissipative\nhydrodynamics ($d$-hydrodynamics) from perfect nonextensive hydrodynamics\n($q$-hydrodynamics) using the nonextensive/dissipative correspondence (NexDC)\nproposed by us recently. The $q$-hydrodynamics can be thus regarded as a\npossible model for the $d$-hydrodynamics facilitating its application to high\nenergy multiparticle production processes. As an example we have shown that\napplying the NexDC to the perfect 1+1 $q$-hydrodynamics, one obtains a proper\ntime evolution of the bulk pressure and the Reynolds number.", "category": "nucl-th" }, { "text": "K anti-K N molecule state with I=1/2 and J^P=1/2^+ studied with\n three-body calculation: A K \\bar{K} N system with I=1/2 and J^P=1/2^+ is investigated with\nnon-relativistic three-body calculations by using effective \\bar K N, K \\bar K\nand KN interactions. The \\bar K N interaction describes the Lambda(1405) as a\n\\bar K N molecule, and the K\\bar K interaction is adjusted to give f_0(980) and\na_0(980) states as K \\bar K molecules. The present investigation suggests that\na bound K \\bar K N state can be formed below the K \\bar K N threshold (1930\nMeV) with a 90 ~ 100 MeV width of three-hadron decays, which are dominated by K\nbar K N -> K pi Sigma and pi eta N. It is found that the K \\bar K N state is a\nweakly bound hadron molecular state with a size larger than an alpha particle\nbecause of the repulsive KN interactions.", "category": "nucl-th" }, { "text": "Hydrodynamics at RHIC -- how well does it work, where and how does it\n break down?: I review the successes and limitations of the ideal fluid dynamic model in\ndescribing hadron emission spectra from Au+Au collisions at the Relativistic\nHeavy Ion Collider (RHIC).", "category": "nucl-th" }, { "text": "Inverse-Reynolds-Dominance approach to transient fluid dynamics: We consider the evolution equations for the bulk viscous pressure, diffusion\ncurrent and shear tensor derived within second-order relativistic dissipative\nhydrodynamics from kinetic theory. By matching the higher order moments\ndirectly to the dissipative quantities, all terms which are of second order in\nthe Knudsen number Kn vanish, leaving only terms of order\n$\\mathcal{O}(\\textrm{Re}^{-1} \\textrm{Kn})$ and $\\mathcal{O}(\\textrm{Re}^{-2})$\nin the relaxation equations, where $\\textrm{Re}^{-1}$ is the inverse Reynolds\nnumber. We therefore refer to this scheme as the Inverse-Reynolds-Dominance\n(IReD) approach. The remaining (non-vanishing) transport coefficients can be\nobtained exclusively in terms of the inverse of the collision matrix. This\nprocedure fixes unambiguously the relaxation times of the dissipative\nquantities, which are no longer related to the eigenvalues of the inverse of\nthe collision matrix. In particular, we find that the relaxation times\ncorresponding to higher-order moments grow as their order increases, thereby\ncontradicting the \\textit{separation of scales} paradigm. The formal (up to\nsecond order) equivalence with the standard DNMR approach is proven and the\nconnection between the IReD transport coefficients and the usual DNMR ones is\nestablished.", "category": "nucl-th" }, { "text": "An implementation of nuclear time-dependent density-functional theory\n and its application to the nuclear isovector electric dipole resonance: Following a previous paper [Y. Shi, Phys. Rev. C 98, 014329(2018)], we\npresent an extension of the density-functional theory to allow for dynamic\ncalculations based on the obtained static Hartree-Fock results. We perform\nextensive benchmark calculations, by comparing the calculated results with that\nof an existing code Sky3D. To perform linear-response calculations using the\nTDDFT method, comparisons have been made with the finite-amplitude\nquasiparticle random-phase approximation (FAM-QRPA) method. We plan to apply\nthe TDDFT method to a systematic description of the IVD resonances in the Zr,\nMo, and Ru isotopes.\n The strengths of IVD resonances are calculated using two complementary\nmethods: TDDFT and FAM-QRPA methods. For the TDDFT results, additional\nbenchmark calculations have been performed using the well-tested code Sky3D. In\nthese three models, the important ingredients which have major influence on the\nresults, such as time-odd potentials, boundary conditions, smoothing\nprocedures, spurious peaks etc., have been carefully examined.\n The current TDDFT and the Sky3D codes yield almost identical response\nfunctions once both codes use the same time-odd mean fields and absorbing\nboundary conditions. The strengths of the IVD resonances calculated using the\nTDDFT and FAM-QRPA methods agree reasonably well with the same position of the\ngiant dipole resonance. Upon seeing a reasonable accuracy offered by the\nimplemented code, we perform systematic TDDFT calculations for spherical Zr and\nMo isotopes near $N=50$, where experimental data exist. For neutron-rich Zr,\nMo, and Ru isotopes where shape evolution exist we predict the photoabsorption\ncross sections based on oblate and triaxial minima.", "category": "nucl-th" }, { "text": "Stability of the $\u03b2$-equilibrated dense matter and core-crust\n transition in neutron stars: The stability of the $\\beta$-equilibrated dense nuclear matter is analyzed\nwith respect to the thermodynamic stability conditions. Based on the density\ndependent M3Y effective nucleon-nucleon interaction, the effects of the nuclear\nincompressibility on the proton fraction in neutron stars and the location of\nthe inner edge of their crusts and core-crust transition density and pressure\nare investigated. The high-density behavior of symmetric and asymmetric nuclear\nmatter satisfies the constraints from the observed flow data of heavy-ion\ncollisions. The neutron star properties studied using $\\beta$-equilibrated\nneutron star matter obtained from this effective interaction for a pure\nhadronic model agree with the recent observations of the massive compact stars.\nThe density, pressure and proton fraction at the inner edge separating the\nliquid core from the solid crust of neutron stars are determined to be\n$\\rho_t=$ 0.0938 fm$^{-3}$, P$_t=$ 0.5006 MeV fm$^{-3}$ and x$_{p(t)}=$ 0.0308,\nrespectively.", "category": "nucl-th" }, { "text": "Comment on piNN Coupling from High Precision np Charge Exchange at 162\n MeV: In this updated and expanded version of our delayed Comment we show that the\nnp backward cross section, as presented by the Uppsala group, is seriously\nflawed (more than 25 sd.). The main reason is the incorrect normalization of\nthe data. We show also that their extrapolation method, used to determine the\ncharged piNN coupling constant, is a factor of about 10 less accurate than\nclaimed by Ericson et al. The large extrapolation error makes the determination\nof the coupling constant by the Uppsala group totally uninteresting.", "category": "nucl-th" }, { "text": "The Proton-Deuteron Break-Up Process in a Three-Dimensional Approach: The pd break-up amplitude in the Faddeev scheme is calculated by employing a\nthree-dimensional method without partial wave decomposition (PWD). In a first\nstep and in view of higher energies only the leading term is evaluated and this\nfor the process d(p,n)pp. A comparison with the results based on PWD reveals\ndiscrepancies in the cross section around 200 MeV. This indicates the onset of\na limitation of the partial wave scheme. Also, around 200 MeV relativistic\neffects are clearly visible and the use of relativistic kinematics shifts the\ncross section peak to where the experimental peak is located. The theoretical\npeak height, however, is wrong and calls first of all for the inclusion of\nrescattering terms, which are shown to be important in a nonrelativistic full\nFaddeev calculation in PWD.", "category": "nucl-th" }, { "text": "$\u03b4$ meson effects on neutron stars in the modified quark-meson\n coupling model: The properties of neutron stars are investigated by including $\\delta$ meson\nfield in the Lagrangian density of modified quark-meson coupling model. The\n$\\Sigma^-$ population with $\\delta$ meson is larger than that without $\\delta$\nmeson at the beginning, but it becomes smaller than that without $\\delta$ meson\nas the appearance of $\\Xi^-$. The $\\delta$ meson has opposite effects on\nhadronic matter with or without hyperons: it softens the EOSes of hadronic\nmatter with hyperons, while it stiffens the EOSes of pure nucleonic matter.\nFurthermore, the leptons and the hyperons have the similar influence on\n$\\delta$ meson effects. The $\\delta$ meson increases the maximum masses of\nneutron stars. The influence of $(\\sigma^*,\\phi)$ on the $\\delta$ meson effects\nare also investigated.", "category": "nucl-th" }, { "text": "Renormalization of nuclear chiral effective field theory with\n non-perturbative leading order interactions: We extend the renormalizability study of the formulation of chiral effective\nfield theory with a finite cutoff, applied to nucleon-nucleon scattering, by\ntaking into account non-perturbative effects. We consider the nucleon-nucleon\ninteraction up to next-to-leading order in the chiral expansion. The\nleading-order interaction is treated non-perturbatively. In contrast to the\npreviously considered case when the leading-order interaction was assumed to be\nperturbative, new features related to the renormalization of the effective\nfield theory are revealed. In particular, more severe constraints on the\nleading-order potential are formulated, which can enforce the renormalizability\nand the correct power counting for the next-to-leading order amplitude. To\nillustrate our theoretical findings, several partial waves in the\nnucleon-nucleon scattering, $^3P_0$, $^3S_1-{^3D_1}$ and $^1S_0$ are analyzed\nnumerically. The cutoff dependence and the convergence of the chiral expansion\nfor those channels are discussed.", "category": "nucl-th" }, { "text": "Momentum Distribution in Nuclear Matter and Finite Nuclei: A simple method is presented to evaluate the effects of short-range\ncorrelations on the momentum distribution of nucleons in nuclear matter within\nthe framework of the Green's function approach. The method provides a very\nefficient representation of the single-particle Green's function for a\ncorrelated system. The reliability of this method is established by comparing\nits results to those obtained in more elaborate calculations. The sensitivity\nof the momentum distribution on the nucleon-nucleon interaction and the nuclear\ndensity is studied. The momentum distributions of nucleons in finite nuclei are\nderived from those in nuclear matter using a local-density approximation. These\nresults are compared to those obtained directly for light nuclei like $^{16}O$.", "category": "nucl-th" }, { "text": "Enlarged deformation region in neutron-rich Zr isotopes by the second\n intruder orbit: Nuclear deformations and density profiles of neutron-rich even-even Zr\nisotopes are investigated using the Skyrme-Hartree-Fock-Bogoliubov method.\nLarge quadrupole and hexadecapole deformations are predicted along with large\nenhancement of the total reaction cross sections at the neutron number\n$N=60$-74. Strong nuclear deformation starting at $N=60$ is induced by the\noccupation of the intruder orbit with the asymptotic quantum number\n$[nn_z\\Lambda]\\Omega$ = [550]1/2 originating from the spherical $0h_{11/2}$\norbit. The deformation region is further enlarged from $N=72$ to 74 owing to\nthe occupation of the next intruder orbit with [530]1/2 originating from the\nspherical $1f_{7/2}$ orbit. This characteristic nuclear deformation is\ncrucially reflected in the systematic behavior of the nuclear radii and the\ndensity profiles near the nuclear surface.", "category": "nucl-th" }, { "text": "Neutral baryonic systems with strangeness: We review the status as regards the existence of three- and four-body bound\nstates made of neutrons and $\\Lambda$ hyperons. For interesting cases, the\ncoupling to neutral baryonic systems made of charged particles of different\nstrangeness has been addressed. There are strong arguments showing that the\n$\\Lambda nn$ system has no bound states. $\\Lambda\\Lambda nn$ strong stable\nstates are not favored by our current knowledge of the strangeness $-1$ and\n$-2$ baryon-baryon interactions. However, a possible $\\Xi^- t$ quasibound state\ndecaying to $\\Lambda\\Lambda nn$ might exist in nature. Similarly, there is a\nbroad agreement about the nonexistence of $\\Lambda\\Lambda n$ bound states.\nHowever, the coupling to $\\Xi NN$ states opens the door to a resonance above\nthe $\\Lambda\\Lambda n$ threshold.", "category": "nucl-th" }, { "text": "Search for time-reversal-invariance violation in double polarized\n antiproton-deuteron scattering: Apart from the $pd$ reaction also the scattering of antiprotons with\ntransversal polarization $p_y^p$ on deuterons with tensor polarization $P_{xz}$\nprovides a null-test signal for time-reversal-invariance violating but parity\nconserving effects. Assuming that the time-reversal-invariance violating $\\bar\nNN$ interaction contains the same operator structure as the $NN$ interaction,\nwe discuss the energy dependence of the null-test signal in $\\bar pd$\nscattering on the basis of a calculation within the spin-dependent Glauber\ntheory at beam energies of 50-300 MeV.", "category": "nucl-th" }, { "text": "Probing halo nucleus structure through intermediate energy elastic\n scattering: This work addresses the question of precisely what features of few body\nmodels of halo nuclei are probed by elastic scattering on protons at high\ncentre-of-mass energies. Our treatment is based on a multiple scattering\nexpansion of the proton-projectile transition amplitude in a form which is well\nadapted to the weakly bound cluster picture of halo nuclei. In the specific\ncase of $^{11}$Li scattering from protons at 800 MeV/u we show that because\ncore recoil effects are significant, scattering crosssections can not, in\ngeneral, be deduced from knowledge of the total matter density alone.\n We advocate that the optical potential concept for the scattering of halo\nnuclei on protons should be avoided and that the multiple scattering series for\nthe full transition amplitude should be used instead.", "category": "nucl-th" }, { "text": "$\u03b1$-Particle Spectrum in the Reaction p+$^{11}$B$\\to \u03b1+\n ^8Be^*\\to 3\u03b1$: Using a simple phenomenological parametrization of the reaction amplitude we\ncalculated $\\alpha$-particle spectrum in the reaction p+$^{11}$B$\\to \\alpha +\n^8Be^*\\to 3\\alpha$ at the resonance proton energy 675 KeV. The parametrization\nincludes Breit-Wigner factor with an energy dependent width for intermediate\n$^8Be^*$ state and the Coulomb and the centrifugal factors in $\\alpha$-particle\nemission vertexes. The shape of the spectrum consists of a well defined peak\ncorresponding to emission of the primary $\\alpha$ and a flat shoulder going\ndown to very low energy. We found that below 1.5 MeV there are 17.5% of\n$\\alpha$'s and below 1 MeV there are 11% of them.", "category": "nucl-th" }, { "text": "A new scheme for heavy nuclei: proxy-SU(3): The SU(3) symmetry realized by J. P. Elliott in the sd nuclear shell is\ndestroyed in heavier shells by the strong spin-orbit interaction. However, the\nSU(3) symmetry has been used for the description of heavy nuclei in terms of\nbosons in the framework of the Interacting Boson Approximation, as well as in\nterms of fermions using the pseudo-SU(3) approximation. We introduce a new\nfermionic approximation, called the proxy-SU(3), and we discuss how some of its\nnovel predictions come out as a consequence of the short range of the\nnucleon-nucleon interaction and the Pauli principle.", "category": "nucl-th" }, { "text": "Verification of Models for Calculation of E1 Radiative Strength: Photoabsorption cross sections and gamma-decay strength function are\ncalculated and compared with experimental data to test the existing models of\ndipole radiative strength functions (RSF) for the middle-weight and heavy\natomic nuclei. Simplified version of the modified Lorentzian model are\nproposed. New tables of giant dipole resonance (GDR) parameters are given. It\nis shown that the phenomenological closed-form models with asymmetric shape can\nbe used for overall estimates of the dipole RSF in the gamma -ray energy region\nup to about 20 MeV when GDR parameters are known or the GDR systematics can be\nadopted. Otherwise, the HFB-QRPA microscopic model and the semi-classical\napproach with moving surface appear to be more adequate methods to estimate the\ndipole photoabsorption RSF.", "category": "nucl-th" }, { "text": "Is perturbative study of ground-state correlations valid?: Perturbative approaches have often been used to include the effects of\nground-state correlations in extended theories of the random-phase\napproximation. Validity of such approaches is investigated for a solvable model\nwhere comparison with exact solutions can be made. It is pointed out that there\nis a case where perturbative approaches give good results in spite of the fact\nthat interaction strength is far beyond a perturbative region.", "category": "nucl-th" }, { "text": "Particle-number projection method in time-dependent Hartree-Fock theory:\n Properties of reaction products: Background: The time-dependent Hartree-Fock (TDHF) theory has been successful\nin describing low-energy heavy ion collisions. Recently, we have shown that\nmultinucleon transfer processes can be reasonably described in the TDHF theory\ncombined with the particle-number projection technique. Purpose: In this work,\nwe propose a theoretical framework to analyze properties of reaction products\nin TDHF calculations. Methods: TDHF calculation in three-dimensional Cartesian\ngrid representation combined with particle number projection method. Results:\nWe develop a theoretical framework to calculate expectation values of operators\nin the TDHF wave function after collision with the particle-number projection.\nTo show how our method works in practice, the method is applied to\n$^{24}$O+$^{16}$O collisions for two quantities, angular momentum and\nexcitation energy. The analyses revealed following features of the reaction:\nThe nucleon removal proceeds gently, leaving small values of angular momentum\nand excitation energy in nucleon removed nuclei. Contrarily, nuclei receiving\nnucleons show expectation values of angular momentum and excitation energy\nwhich increase as the incident energy increases. Conclusions: We have developed\na formalism to analyze properties of fragment nuclei in the TDHF theory\ncombined with the particle-number projection technique. The method will be\nuseful for microscopic investigations of reaction mechanisms in low-energy\nheavy ion collisions as well as for evaluating effects of particle evaporation\non multinucleon transfer cross sections.", "category": "nucl-th" }, { "text": "Faddeev-type calculation of eta-d threshold scattering: The scattering length for the eta-meson collision with deuteron is calculated\non the basis of rigorous few-body equations (AGS) for various eta-N input. The\nresults obtained strongly support the existence of a resonance or quasi-bound\nstate close to the eta-d threshold.", "category": "nucl-th" }, { "text": "The $\u03c0\u03c1$ Cloud Contribution to the $\u03c9$ Width in Nuclear Matter: The width of the $\\omega$ meson in cold nuclear matter is computed in a\nhadronic many-body approach, focusing on a detailed treatment of the medium\nmodifications of intermediate $\\pi\\rho$ states. The $\\pi$ and $\\rho$\npropagators are dressed by their selfenergies in nuclear matter taken from\npreviously constrained many-body calculations. The pion selfenergy includes\n$Nh$ and $\\Delta h$ excitations with short-range correlations, while the $\\rho$\nselfenergy incorporates the same dressing of its $2\\pi$ cloud with a full\n3-momentum dependence and vertex corrections, as well as direct resonance-hole\nexcitations; both contributions were quantitatively fit to total\nphoto-absorption spectra and $\\pi N\\to\\rho N$ scattering. Our calculations\naccount for in-medium decays of type $\\omega N\\to \\pi N^{(*)}, \\pi\\pi\nN(\\Delta)$, and 2-body absorptions $\\omega NN\\to NN^{(*)},\\pi NN$. This causes\ndeviations of the in-medium $\\omega$ width from a linear behavior in density,\nwith important contributions from spacelike $\\rho$ propagators. The $\\omega$\nwidth from the $\\rho\\pi$ cloud may reach up to 200 MeV at normal nuclear matter\ndensity, with a moderate 3-momentum dependence. This largely resolves the\ndiscrepancy of linear $T$-$\\varrho$ approximations with the values deduced from\nnuclear photoproduction measurements.", "category": "nucl-th" }, { "text": "In-medium $\u039b$ isospin impurity from charge symmetry breaking in\n the ${_\u039b^4}{\\rm H}-{_\u039b^4}{\\rm He}$ mirror hypernuclei: The $\\Lambda$ separation energies in the mirror hypernuclei\n${_{\\Lambda}^4}{\\rm H}-{_{\\Lambda}^4}{\\rm He}$ exhibit large charge symmetry\nbreaking (CSB). Analyzing this CSB within pionless effective field theory while\nusing partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a\n$\\Lambda -\\Sigma^0$ induced in-medium admixture amplitude ${\\cal\nA}_{I=1}\\approx 1.5\\%$ in the dominantly isospin $I=0$ $\\Lambda$ hyperon. Our\nresults confirm the free-space value ${\\cal A}^{(0)}_{I=1}$ inferred directly\nwithin the SU(3) baryon octet by Dalitz and von-Hippel in 1964 and reaffirmed\nin a recent QCD+QED lattice calculation. Furthermore, exploring the\nconsequences of SU(3) flavor symmetry on the $\\Lambda$-nucleon interaction, we\nfind that CSB is expected to impact the $S=1$ and $S=0$ spin channels in\nopposite directions, with the latter dominating by an order of magnitude. These\nobservations explain a recent deduction of $\\Lambda$-nucleon CSB strengths.", "category": "nucl-th" }, { "text": "Charge Form Factor and Cluster Structure of $^6$Li Nucleus: The charge form factor of ${}^6$Li nucleus is considered on the basis of its\ncluster structure. The charge density of ${}^6$Li is presented as a\nsuperposition of two terms. One of them is a folded density and the second one\nis a sum of ${}^4$He and the deuteron densities. Using the available\nexperimental data for ${}^4$He and deuteron charge form factors, a good\nagreement of the calculations within the suggested scheme is obtained with the\nexperimental data for the charge form factor of ${}^6$Li, including those in\nthe region of large transferred momenta.", "category": "nucl-th" }, { "text": "Threshold $\u03c0^0$ photoproduction in relativistic chiral perturbation\n theory: We present a calculation of $\\pi^0$ photoproduction on the proton in\nmanifestly Lorentz-invariant baryon chiral perturbation theory up to and\nincluding chiral order $q^4$. With the results we analyze the latest $\\pi^0$\nphotoproduction data in the threshold region obtained at the Mainz Microtron.\nIn the calculation of observables and the fit of the low-energy constants, we\ntake $S$, $P$, and $D$ waves into account. We compare the results for the\nmultipoles with the corresponding single-energy analysis. Furthermore, we also\nfit the $O(q^4)$ heavy-baryon chiral perturbation theory calculation and\ncompare both results. We provide predictions for several polarization\nobservables for future experiments. Finally, we discuss the $\\beta$ parameter\nof the unitarity cusp which is related to the breaking of isospin symmetry.", "category": "nucl-th" }, { "text": "Shape of atomic nuclei in heavy ion collisions: In the hydrodynamic model description of heavy ion collisions, the\nfinal-state anisotropic flow $v_n$ are linearly related to the strength of the\nmulti-pole shape of the distribution of nucleons in the transverse plane\n$\\varepsilon_n$, $v_n\\propto \\varepsilon_n$. The $\\varepsilon_n$, for\n$n=1,2,3,4$, are sensitive to the shape of the colliding ions, characterized by\nthe quadrupole $\\beta_2$, octupole $\\beta_3$ and hexadecapole $\\beta_4$\ndeformations. This sensitivity is investigated analytically and also in a Monte\nCarlo Glauber model. One observes a robust linear relation,\n$\\langle\\varepsilon_n^2\\rangle = a_n'+b_n'\\beta_n^2$, for events in a fixed\ncentrality. The $\\langle\\varepsilon_1^2\\rangle$ has a contribution from\n$\\beta_3$ and $\\beta_4$, and $\\langle\\varepsilon_3^2\\rangle$ from $\\beta_4$. In\nthe ultra-central collisions, there are little cross contributions between\n$\\beta_2$ and $\\varepsilon_3$ and between $\\beta_3$ and $\\varepsilon_2$, but\nclear cross contributions are present in non-central collisions. Additionally,\n$\\langle\\varepsilon_n^2\\rangle$ are insensitive to non-axial shape parameters\nsuch as the triaxiality. This is good news because the measurements of $v_2$,\n$v_3$ and $v_4$ can be used to constrain simultaneously the $\\beta_2$,\n$\\beta_3$, and $\\beta_4$ values. This is best done by comparing two colliding\nions with similar mass numbers and therefore nearly identical $a_n'$, to obtain\nsimple equation that relates the $\\beta_n$ of the two species. This opens up\nthe possibility to map the shape of the atomic nuclei at a timescale\n($<10^{-24}$s) much shorter than probed by low-energy nuclear structure physics\n($<10^{-21}$s), which ultimately may provide information complementary to those\nobtained in the nuclear structure experiments.", "category": "nucl-th" }, { "text": "Initializing BSQ with Open-Source ICCING: While it is well known that there is a significant amount of conserved\ncharges in the initial state of nuclear collisions, the production of these due\nto gluon splitting has yet to be thoroughly investigated. The ICCING (Initial\nConserved Charges in Nuclear Geometry) algorithm reconstructs these quark\ndistributions, providing conserved strange, baryon, and electric charges, by\nsampling a given model for the $g \\rightarrow q\\bar{q}$ splitting function over\nthe initial energy density, which is valid at top collider energies, even when\n$\\mu_B=0$. The ICCING algorithm includes fluctuations in the gluon longitudinal\nmomenta, a structure that supports the implementation of dynamical processes,\nand the c++ version is now open-source. A full analysis of parameter choices on\nthe model has been done to quantify the effect these have on the underlying\nphysics. We find there is a sustained difference across the different charges\nthat indicates sensitivity to hot spot geometry.", "category": "nucl-th" }, { "text": "Diffuseness parameter as a bottleneck for accurate half-life\n calculations: An investigation of the calculated $\\alpha$ decay half-lives of super heavy\nnuclei (SHN) reveals that the diffuseness parameter is a great bottleneck for\nachieving accurate results and predictions. In particular, when universal\nproximity function is adopted for nuclear potential, half-life is found to vary\nsignificantly and nonlinearly as a function of diffuseness parameter. To\novercome this limiting hurdle, a new semiempirical formula for diffuseness that\nis dependent on charge and neutron numbers is proposed in this work. With the\nmodel at hand, half-lives of 218 SHN are computed, for 68 of which there exists\navailable experimental data and 150 of which are predicted. The calculations of\nhalf-lives for 68 SHN are compared against experimental data and the calculated\ndata obtained by using deformed Woods-Saxon, deformed Coulomb potentials model,\nand six semiempirical formulas. The predictions of 150 SHN are compared against\nthe predictions of seven of the current best semiempirical formulas.\nCalculations of the present study are in good agreement with the experimental\nhalf-lives outperforming all but ImSahu semiempirical formula. Moreover, the\npredictions of our model are consistent with predictions of the semiempirical\nformulas. We strongly conclude that more attention should be directed toward\nobtaining accurate diffuseness parameter values for using it in nuclear\ncalculations.", "category": "nucl-th" }, { "text": "Properties of nuclear pastas: In this Review we study the nuclear pastas as they are expected to be formed\nin neutron star cores. We start with a study of the pastas formed in nuclear\nmatter (composed of protons and neutrons), we follow with the role of the\nelectron gas on the formation of pastas, and we then investigate the pastas in\nneutron star matter (nuclear matter embedded in an electron gas).", "category": "nucl-th" }, { "text": "Direct capture in the $^{130}$Sn(n,$\u03b3$)$^{131}$Sn and\n $^{132}$Sn(n,$\u03b3$)$^{133}$Sn reactions under $r$-process conditions: The cross sections of the $^{130}$Sn(n,$\\gamma$)$^{131}$Sn and\n$^{132}$Sn(n,$\\gamma$)$^{133}$Sn reactions are calculated in the direct capture\nmodel at low energies below 1.5\\,MeV. Using recent data from (d,p) transfer\nexperiments on $^{130}$Sn and $^{132}$Sn, it is possible to avoid global input\nparameters with their inherent uncertainties and to determine all input to the\ndirect capture model by local adjustments. The calculated direct capture cross\nsections of $^{130}$Sn and $^{132}$Sn are almost identical and have\nuncertainties of less than a factor of two. The stellar reaction rates $N_A <\n\\sigma v >$ show a slight increase with temperature. Finally an estimate for\nthe influence of low-lying resonances to the stellar reaction rates is given.", "category": "nucl-th" }, { "text": "Neutrino-nucleus reactions on ^{12}C and ^{16}O: Exclusive and inclusive $(\\nu_\\mu, \\mu^-), (\\nu_e, e^-)$ cross-sections and\n$\\mu^-$-capture rates are calculated for ^{12}C and ^{16}O using the consistent\nrandom phase approximation (RPA) and pairing model. After a pairing correction\nis introduced to the RPA results the flux-averaged theoretical $(\\nu_\\mu,\n\\mu^-), (\\nu_e, e^-)$ cross-sections and $\\mu^-$-capture rates in $^{12}$C are\nin good agreement with experiment. In particular when one takes into account\nthe experimental error bars, the recently measured range of values for the\n$(\\nu_\\mu, \\mu^-)$ cross-section is in agreement with the present theoretical\nresults. Predictions of $(\\nu_\\mu, \\mu^-)$ and $(\\nu_e, e^-)$ cross-sections in\n^{16}O are also presented.", "category": "nucl-th" }, { "text": "Rescaling of Nuclear Structure Functions: It is shown that nucleonic structure functions are $x-$ and $Q^{2}-$rescaled\nin nuclei. The $x-$rescaling accounts for nuclear effects in the case of exact\nscaling, while the $Q^{2}-$rescaling is responsible for a corresponding\nmodification of quantum corrections. This result is obtained in the leading\norder for all flavour combinations and connects the two known models for the\nEMC-effect. Electroproduction and gluonic nuclear structure functions are\ncalculated.", "category": "nucl-th" }, { "text": "On the complexion of pseudoscalar mesons: A strongly momentum-dependent dressed-quark mass function is basic to QCD. It\nis central to the appearance of a constituent-quark mass-scale and an\nexistential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSEs)\nstudies have long emphasised this importance, and have proved that QCD's\nGoldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic\ndecay constant in the chiral limit when chiral symmetry is dynamically broken,\nwhile the decay constants of their radial excitations vanish. Such features are\nreadily illustrated using a rainbow-ladder truncation of the DSEs. In this\nconnection we find (in GeV): f_{eta_c(1S)}= 0.233, m_{eta_c(2S)}=3.42; and\nsupport for interpreting eta(1295), eta(1470) as the first radial excitations\nof eta(548), eta'(958), respectively, and K(1460) as the first radial\nexcitation of the kaon. Moreover, such radial excitations have electromagnetic\ndiameters greater than 2fm. This exceeds the spatial length of lattices used\ntypically in contemporary lattice-QCD.", "category": "nucl-th" }, { "text": "Limits on the neutrino mass from neutrinoless double-$\u03b2$ decay: Neutrinoless double-$\\beta$ decay is of fundamental importance for the\ndetermining neutrino mass. By combining a calculation of nuclear matrix\nelements within the framework of the microscopic interacting boson model\n(IBM-2) with an improved calculation of phase space factors, we set limits on\nthe average light neutrino mass and on the average inverse heavy neutrino mass\n(flavor violating parameter).", "category": "nucl-th" }, { "text": "Applications of the chiral potential with the semi-local regularization\n in momentum space to the disintegration processes: We apply the chiral potential with the momentum space semi-local\nregularization to the $^2$H and $^3$He photodisintegration processes and to the\n(anti)neutrino induced deuteron breakup reactions. Specifically, the\ndifferential cross section, the photon analyzing power and the final proton\npolarization have been calculated for the deuteron photodisintegration at the\nphoton energies 30 MeV and 100 MeV. For the $^3$He photodisintegration\npredictions for the semi-inclusive and exclusive differential cross sections\nare presented for the photon energies up to 120 MeV. The total cross section is\ncalculated for the (anti)neutrino disintegrations of the deuteron for the\n(anti)neutrino energies below 200 MeV. The predictions based on the Argonne V18\npotential or on the older chiral force with regularization applied in\ncoordinate space are used for comparison. Using the fifth order chiral\nnucleon-nucleon potential supplemented with dominant contributions from the\nsixth order allows us to obtain converged predictions for the regarded\nreactions and observables. Our results based on the newest semi-local chiral\npotentials show even smaller cutoff dependence for the considered electroweak\nobservables than the previously reported ones with a coordinate-space\nregulator. However, some of the studied polarization observables in the\ndeuteron photodisintegration process reveal more sensitivity to the regulator\nvalue than the unpolarized cross section. The chiral potential regularized\nsemi-locally in momentum space yields also fast convergence of results with the\nchiral order. These features make the used potential a high quality tool to\nstudy electroweak processes.", "category": "nucl-th" }, { "text": "Momentum-space treatment of Coulomb interaction in three-nucleon\n reactions with two protons: The Coulomb interaction between the two protons is included in the\ncalculation of proton-deuteron elastic scattering, radiative proton-deuteron\ncapture and two-body electromagnetic disintegration of ${}^3\\mathrm{He}$. The\nhadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn\npotential and its realistic extension CD Bonn + $\\Delta$ to a coupled-channel\ntwo-baryon potential, allowing for single virtual $\\Delta$-isobar excitation.\nCalculations are done using integral equations in momentum space. The screening\nand renormalization approach is employed for including the Coulomb interaction.\nConvergence of the procedure is found already at moderate screening radii. The\nreliability of the method is demonstrated. The Coulomb effect on observables is\nseen at low energies for the whole kinematic regime. In proton-deuteron elastic\nscattering at higher energies the Coulomb effect is confined to forward\nscattering angles; the $\\Delta$-isobar effect found previously remains\nunchanged by Coulomb. In electromagnetic reactions Coulomb competes with other\neffects in a complicated way.", "category": "nucl-th" }, { "text": "Ab initio computation of the longitudinal response function in $^{40}$Ca: We present a consistent \\emph{ab initio} computation of the longitudinal\nresponse function $R_L$ in $^{40}$Ca using the coupled-cluster and Lorentz\nintegral transform methods starting from chiral nucleon-nucleon and\nthree-nucleon interactions. We validate our approach by comparing our results\nfor $R_L$ in $^4$He and the Coulomb sum rule in $^{40}$Ca against experimental\ndata and other calculations. For $R_L$ in $^{40}$Ca we obtain a very good\nagreement with experiment in the quasi-elastic peak up to intermediate momentum\ntransfers, and we find that final state interactions are essential for an\naccurate description of the data. This work presents a milestone towards\n\\emph{ab initio} computations of neutrino-nucleus cross sections relevant for\nexperimental long-baseline neutrino programs.", "category": "nucl-th" }, { "text": "Partial Dynamical SU(3) Symmetry and the Nature of the Lowest K=0\n Collective Excitation in Deformed Nuclei: We discuss the implications of partial dynamical SU(3) symmetry (PDS) for the\nstructure of the lowest K=0^{+} (K=0_2) collective excitation in deformed\nnuclei. We consider an interacting boson model Hamiltonian whose ground and\ngamma bands have good SU(3) symmetry while the K=0_2 band is mixed. It is shown\nthat the double-phonon components in the K=0_2 wave function arise from SU(3)\nadmixtures which, in turn, can be determined from absolute E2 rates connecting\nthe K=0_2 and ground bands. An explicit expression is derived for these\nadmixtures in terms of the ratio of K=0_2 and gamma bandhead energies. The\nSU(3) PDS predictions are compared with existing data and with broken-SU(3)\ncalculations for ^{168}Er.", "category": "nucl-th" }, { "text": "Improved Kelson-Garvey mass relations for proton-rich nuclei: The improved Kelson-Garvey (ImKG) mass relations are proposed from the mass\ndifferences of mirror nuclei. The masses of 31 measured proton-rich nuclei with\n$7\\leq A\\leq41$ and $-5\\leq (N-Z)\\leq-3$ can be remarkably well reproduced by\nusing the proposed relations, with a root-mean-square deviation of 0.398 MeV,\nwhich is much smaller than the results of Kelson-Garvey (0.502 MeV) and\nIsobar-Mirror mass relations (0.647 MeV). This is because many more masses of\nparticipating nuclei are involved in the ImKG mass relations for predicting the\nmasses of unknown proton-rich nuclei. The masses for 144 unknown proton-rich\nnuclei with $6\\leq A\\leq74$ are predicted by using the ImKG mass relations. The\none- and two-proton separation energies for these proton-rich nuclei and the\ndiproton emission are investigated simultaneously.", "category": "nucl-th" }, { "text": "Derivation of breakup probabilities from experimental elastic\n backscattering data: We suggest simple and useful method to extract breakup probabilities from the\nexperimental elastic backscattering probabilities in the reactions with toughly\nand weakly bound nuclei.", "category": "nucl-th" }, { "text": "Microscopic Optical Potentials for Helium-6 Scattering off Protons: The differential cross section and the analyzing power are calculated for\nelastic scattering of $^6$He from a proton target using a microscopic folding\noptical potential, in which the $^6$He nucleus is described in terms of a\n$^4$He-core with two additional neutrons in the valence p-shell. In contrast to\nprevious work of that nature, all contributions from the interaction of the\nvalence neutrons with the target protons are taken into account.", "category": "nucl-th" }, { "text": "Global superscaling analysis of quasielastic electron scattering with\n relativistic effective mass: We present a global analysis of the inclusive quasielastic electron\nscattering data with a superscaling approach with relativistic effective mass.\nThe SuSAM* model exploits the approximation of factorization of the scaling\nfunction $f^*(\\psi^*)$ out of the cross section under quasifree conditions. Our\napproach is based on the relativistic mean field theory of nuclear matter where\na relativistic effective mass for the nucleon encodes the dynamics of nucleons\nmoving in presence of scalar and vector potentials. Both the scaling variable\n$\\psi^*$ and the single nucleon cross sections include the effective mass as a\nparameter to be fitted to the data alongside the Fermi momentum $k_F$. Several\nmethods to extract the scaling function and its uncertainty from the data are\nproposed and compared. The model predictions for the quasielastic cross section\nand the theoretical error bands are presented and discussed for nuclei along\nthe periodic table from $A=2$ to $A=238$: $^2$H, $^3$H, $^3$He, $^4$He,\n$^{12}$C, $^{6}$Li, $^{9}$Be, $^{24}$Mg, $^{59}$Ni,\n $^{89}$Y, $^{119}$Sn, $^{181}$Ta, $^{186}$W, $^{197}$Au, $^{16}$O, $^{27}$Al,\n$^{40}$Ca, $^{48}$Ca, $^{56}$Fe, $^{208}$Pb, and $^{238}$U.\n We find that more than 9000 of the total $\\sim 20000$ data fall within the\nquasielastic theoretical bands. Predictions for $^{48}$Ti and $^{40}$Ar are\nalso provided for the kinematics of interest to neutrino experiments.", "category": "nucl-th" }, { "text": "A ferro-deformation at the open quantum system with protons, Z = 8,\n neutrons, N = 20: 28O: We offer a possibility that the nuclear system with protons, Z = 8 has a\nlarge deformation at neutrons, N = 20; 28O that is beyond the neutron drip\nline. According to our previous works [arXiv: 1604.05013, 1604.02786,\n1604.01017], it is expected that the ferro-deformation would occur at Z = 8, N\n= 20 through a shape phase transition at N = 18 out of N =16. The shape\ntransition can be explained in terms of isospin dependent spin-orbital\ninteractions between neutrons in the d3/2 orbital and protons in the d5/2\norbital, by yielding both the neutron and the proton pseudo-shell\nconfigurations built on each combined subshells. We argue that such a large\ndeformation at N = 18 would be responsible for the 26O to be unbound, leading\nto a ground state neutron emitter. The ferro-deformation is mapped on the\nnuclear chart such that is around the following critical proton, neutron\ncoordinates, (Z, N); (64, 104), (40, 64), (20, 40), (8, 20). This configuration\ndepicts a beautiful pattern coming from a harmonious order in the microscopic\nquantum world.", "category": "nucl-th" }, { "text": "A study of the correlations between jet quenching observables at RHIC: Focusing on four types of correlation plots, $R_{\\rm AA}$ vs. $v_2$, $R_{\\rm\nAA}$ vs. $I_{\\rm AA}$, $I_{\\rm AA}$ vs. $v_2^{I_{\\rm AA}}$ and $v_2$ vs.\\\n$v_2^{I_{\\rm AA}}$, we demonstrate how the centrality dependence of\n\\emph{correlations} between multiple jet quenching observables provide valuable\ninsight into the energy loss mechanism in a quark-gluon plasma. In particular\nwe find that a qualitative energy loss model gives a good description of\n$R_{\\rm AA}$ vs.\\ $v_2$ only when we take $\\Delta E\\sim l^3$ and a medium\ngeometry generated by a model of the Color Glass Condensate. This same $\\Delta\nE\\sim l^3$ model also qualitatively describes the trigger $p_T$ dependence of\n$R_{\\rm AA}$ vs.\\ $I_{\\rm AA}$ data and makes novel predictions for the\ncentrality dependence for this $R_{\\rm AA}$ vs.\\ $I_{\\rm AA}$ correlation.\nCurrent data suggests, albeit with extremely large uncertainty, that\n$v_2^{I_{\\rm AA}}\\gg v_2$, a correlation that is difficult to reproduce in\ncurrent energy loss models.", "category": "nucl-th" }, { "text": "Two-nucleon knockout contributions to the $^{12}$C$(e,e'p)$ reaction in\n the dip and {$\u0394$}(1232) regions: The contributions from $^{12}$C$(e,e'pn)$ and $^{12}$C$(e,e'pp)$ to the\nsemi-exclusive $^{12}$C$(e,e'p)$ cross section have been calculated in an\nunfactorized model for two-nucleon emission. We assume direct two-nucleon\nknockout after virtual photon coupling with the two-body pion-exchange currents\nin the target nucleus. Results are presented at several kinematical conditions\nin the dip and $\\Delta$(1232) regions. The calculated two-nucleon knockout\nstrength is observed to account for a large fraction of the measured $(e,e'p)$\nstrength above the two-nucleon emission threshold.", "category": "nucl-th" }, { "text": "Vacuum creation of quarks at the time scale of QGP thermalization and\n strangeness enhancement in heavy-ion collisions: The vacuum parton creation in quickly varying external fields is studied at\nthe time scale of order 1 fm/$c$ typical for the quark-gluon plasma formation\nand thermalization. To describe the pre-equilibrium evolution of the system the\ntransport kinetic equation is employed. It is shown that the dynamics of\nproduction process at times comparable with particle inverse masses can deviate\nconsiderably from that based on classical Schwinger-like estimates for\nhomogeneous and constant fields. One of the effects caused by non-stationary\nchromoelectric fields is the enhancement of the yield of $s\\bar{s}$ quark\npairs. Dependence of this effect on the shape and duration of the field pulse\nis studied together with the influence of string fusion and reduction of quark\nmasses.", "category": "nucl-th" }, { "text": "$0^+$ to $2^+$ neutrinoless double-$\u03b2$ decay of $^{76}$Ge,\n $^{82}$Se, $^{130}$Te and $^{136}$Xe in the microscopic interacting boson\n model}: Here, we study the neutrinoless double-$\\beta$ ($0\\nu\\beta\\beta$) decay\nbetween the ground state and the first $2^+$ state of $^{76}\\mbox{Ge}\n\\rightarrow {}^{76}\\mbox{Se}$, $^{82}\\mbox{Se} \\rightarrow{}^{82}\\mbox{Kr}$,\n$^{130}\\mbox{Te} \\rightarrow {}^{130}\\mbox{Xe}$ and $^{136}\\mbox{Xe}\n\\rightarrow {}^{136}\\mbox{Ba}$ systems. The relevant nuclear matrix elements\n(NMEs) involved in the process are calculated within the formalism of the\nmicroscopic interacting boson model (IBM-2). The IBM-2 has been widely used to\nobtain predictions for nuclear observables, such as the spectrum, but also to\nexplore the possible emergence of beyond-the-Standard Model effects in the weak\ninteractions of nuclei. Our calculations are carried out by considering the\nexchange of a Majorana neutrino between two nucleons ($2N$-mechanism). In\naddition to NMEs, we calculate the associated leptonic phase-space factors\n(PSFs) using electron radial wave functions, which are obtained by solving\nnumerically the Dirac equation of a screened Coulomb potential that takes into\naccount finite nuclear size. By combining our IBM-2 results for the NMEs with\nthose for the PSFs along with experimental half-life limits, we can set limits\non the $\\langle \\lambda \\rangle$ and $\\langle \\eta \\rangle$ couplings of\nleft-right (L-R) models.", "category": "nucl-th" }, { "text": "Role of the isospin diffusion on cluster transfer in $^{12,14}$C +\n $^{209}$Bi reactions: Heavy-ion collisions at near-barrier energies provide a crucial pathway for\ninvestigating nucleon correlations and clustering structures.\n Recent experimental results showed that the valence neutrons in light\nprojectiles obviously enhance the $\\alpha$ transfer. This finding is extremely\npuzzled and fascinating, because it violates the ground-state $Q$ value\nsystematics unexpectedly. In this work, the time-dependent Hartree-Fock\napproach is utilized to investigate the cluster transfer. By comparing the\nreactions $^{12,14}$C + $^{209}$Bi, we discover that above puzzling behavior is\nbecause of the strong correlation between isospin diffusion and clustering. Our\ncalculations clearly show that the equilibrium of neutron-to-proton ratio\nstrongly inhibits the clustering. This work opens a prospect for investigating\nthe clustering in open quantum system.", "category": "nucl-th" }, { "text": "How well do we understand Beryllium-7 + proton -> Boron-8 + photon? An\n Effective Field Theory perspective: We have studied the 7Be(p,photon)8B reaction in the Halo effective field\ntheory (EFT) framework. The leading order (LO) results were published in\nPhys.Rev.C89,051602(2014) after the isospin mirror process, 7Li(n,photon)8Li,\nwas addressed in Phys.Rev.C89,024613(2014). In both calculations, one key step\nwas using the final shallow bound state asymptotic normalization coefficients\n(ANCs) computed by ab initio methods to fix the EFT couplings. Recently we have\ndeveloped the next-to-LO (NLO) formalism (to appear soon), which could\nreproduce other model results by no worse than 1% when the 7Be-p energy was\nbetween 0 and 0.5 MeV. In our recent report (arXiv:1507.07239), a different\napproach from that in Phys.Rev.C89,051602(2014) was used. We applied Bayesian\nanalysis to constrain all the NLO-EFT parameters based on measured S-factors,\nand found tight constraints on the S-factor at solar energies. Our S(E=0 MeV)=\n21.3 + - 0.7 eV b. The uncertainty is half of that previously recommended. In\nthis proceeding, we provide extra details of the Bayesian analysis, including\nthe computed EFT parameters' probability distribution functions (PDFs) and how\nthe choice of input data impacts final results.", "category": "nucl-th" }, { "text": "3- and 4- body meson- nuclear clusters: The binding energies and matter distributions for the 3- body systems like\n$\\phi$- meson + 2N, 2$\\phi$ + N and 4- body system like $\\phi$+3n are\ncalculated. For the 3- particle systems two- dimensional Faddeev equations in\nthe differential form are used. For the 4- body system $\\phi$+3n the folding\nmodel is applied.", "category": "nucl-th" }, { "text": "The resonance absorption probability function for neutron and\n multiplicative integral: The analytical approximations for the moderating neutrons flux density like\nFermi spectra, widely used in reactor physics, involve the probability function\nfor moderating neutron to avoid the resonant absorption obtained using some\nrestrictive assumptions regarding the acceptable resonances width. By means of\nmultiplicative integral (Volterra integral) theory for a commutative algebra an\nanalytical expression for the probability function is obtained rigorously\nwithout any restrictive assumptions.", "category": "nucl-th" }, { "text": "Periodic orbit bifurcations and local symmetry restorations in\n exotic-shape nuclear mean fields: The semiclassical origins of the enhancement of shell effects in exotic-shape\nmean-field potentials are investigated by focusing attention on the roles of\nthe local symmetries associated with the periodic-orbit bifurcations. The\ndeformed shell structures for four types of pure octupole shapes in the nuclear\nmean-field model having a realistic radial dependence are analyzed. Remarkable\nshell effects are shown for a large Y32 deformation having tetrahedral\nsymmetry. Much stronger shell effects found in the shape parametrization\nsmoothly connecting the sphere and the tetrahedron are investigated from the\nview point of the classical-quantum correspondence. The local dynamical\nsymmetries associated with the bridge orbit bifurcations are shown to have\nsignificant roles in emergence of the exotic deformed shell structures for\ncertain combinations of the surface diffuseness and the tetrahedral deformation\nparameters.", "category": "nucl-th" }, { "text": "Deuteron disintegration in three dimensions: We compare results from the traditional partial wave treatment of deuteron\nelectro-disintegration with a new approach that uses three dimensional\nformalism. The new framework for the two-nucleon (2N) system using a complete\nset of isospin - spin states made it possible to construct simple\nimplementations that employ a very general operator form of the current\noperator and 2N states.", "category": "nucl-th" }, { "text": "Newly Evaluated Neutron Reaction Data on Chromium Isotopes: Neutron reaction data for the set of major chromium isotopes were reevaluated\nfrom the thermal energy range up to 20 MeV. In the low energy region, updates\nto the thermal values together with an improved $R$-matrix analysis of the\nresonance parameters characterizing the cluster of large $s$-wave resonances\nfor $^{50,53}$Cr isotopes were performed. In the intermediate and high energy\nrange up to 20 MeV, the evaluation methodology used statistical nuclear\nreaction models implemented in the EMPIRE code within the Hauser-Feshbach\nframework to evaluate the reaction cross sections and angular distributions.\nExceptionally, experimental data were used to evaluate relevant cross sections\nabove the resonance region up to 5 MeV in the major $^{52}$Cr isotope.\nEvaluations were benchmarked with Monte Carlo simulations of a small suite of\ncritical assemblies highly sensitive to Chromium data, and with the Oktavian\nshielding benchmark to judge deep penetration performance with a 14-MeV D-T\nneutron source. A significant improvement in performance is demonstrated\ncompared to existing evaluations.", "category": "nucl-th" }, { "text": "Searching for small droplets of hydrodynamic fluid in proton--proton\n collisions at the LHC: In this paper, we investigate the hydrodynamic collectivity in\nhigh-multiplicity events of proton-proton collisions at $\\sqrt{s}=$ 13 TeV,\nusing iEBE-VISHNU hybrid model with three different initial conditions, namely,\nHIJING, super-MC and TRENTo. With properly tuned parameters, hydrodynamic\nsimulations with each initial model give reasonable descriptions of the\nmeasured two-particle correlations, including the integrated and $p_{\\rm\nT}$-differential flow for all charged and identified hadrons. However, the\nhydrodynamic simulations fail to describe the negative value of the\nfour-particle cumulant $c_2^v\\{4\\}$ as measured in experiments. Further\ninvestigations show that the non-linear response between the elliptic flow\n$v_2$ and the initial eccentricity $\\varepsilon_2$ becomes significant in the\nsmall p-p systems. This leads to a large deviation from linear eccentricity\nscaling and generates additional flow fluctuations, which results in a positive\n$c_2^v\\{4\\}$ even with a negative $c_2^\\varepsilon\\{4\\}$ from the initial\nstate. We also presented the first hydrodynamic calculations of multi-particle\nmixed harmonic azimuthal correlations in p-p collisions, such as normalized\nasymmetric cumulant $nac_n\\{3\\}$, normalized Symmetric-Cumulant,\n$nsc_{2,3}\\{4\\}$ and $nsc_{2,4}\\{4\\}$. Although many qualitative features are\nreproduced by the hydrodynamic simulations with chosen parameters, the measured\nnegative $nsc_{2,3}\\{4\\}$ cannot be reproduced. The failure of the description\nof negative $c_2\\{4\\}$ and $nsc_{2,3}\\{4\\}$ triggers the question on whether\nhydrodynamics with a fundamentally new initial state model could solve this\npuzzle, or hydrodynamics itself might not be the appreciated mechanism of the\nobserved collectivity in p-p collisions at the LHC.", "category": "nucl-th" }, { "text": "Phase transition of the nucleon-antinucleon plasma at different ratios: We investigate phase transitions for the Walecka model at very high\ntemperatures. As is well known, depending on the parametrization of this model\nand for the particular case of a zero chemical potential ($ \\mu $), a first\norder phase transition is possible \\cite{theis}. We investigate this model for\nthe case in which $ \\mu \\ne 0 $. It turns out that, in this situation, phases\nwith different values of antinucleon-nucleon ratios and net baryon densities\nmay coexist. We present the temperature versus antinucleon-nucleon ratio as\nwell as the temperature versus the net baryon density for the coexistence\nregion. The temperature versus chemical potential phase diagram is also\npresented.", "category": "nucl-th" }, { "text": "Symmetries at and Near Critical Points of Quantum Phase Transitions in\n Nuclei: We examine several types of symmetries which are relevant to quantum phase\ntransitions in nuclei. These include: critical-point, quasidynamical, and\npartial dynamical symmetries.", "category": "nucl-th" }, { "text": "Strictly finite-range potential for light and heavy nuclei: Strictly finite-range (SFR) potentials are exactly zero beyond their finite\nrange. Single-particle energies and densities as well as S-matrix pole\ntrajectories are studied in a few SFR potentials suited for the description of\nneutrons interacting with light and heavy nuclei. The SFR potentials considered\nare the standard cut-off Woods--Saxon (CWS) potentials and two potentials\napproaching zero smoothly: the SV potential introduced by Salamon and Vertse\nand the SS potential of Sahu and Sahu. The parameters of these latter were set\nso that the potentials may be similar to the CWS shape. The range of the SV and\nSS potentials scales with the cube root of the mass number of the core like the\nnuclear radius itself. For light nuclei a single term of the SV potential (with\na single parameter) is enough for a good description of the neutron-nucleus\ninteraction. The trajectories are compared with a bench-mark for which the\nstarting points (belonging to potential depth zero) can be determined\nindependently. Even the CWS potential is found to conform to this bench-mark if\nthe range is identified with the cutoff radius. For the CWS potentials some\ntrajectories show irregular shapes, while for the SV and SS potentials all\ntrajectories behave regularly.", "category": "nucl-th" }, { "text": "Extracting $\u03c3_{\u03c0N}$ from pionic atoms: We discuss a recent extraction of the $\\pi N$ $\\sigma$ term $\\sigma_{\\pi N}$\nfrom a large-scale fit of pionic-atom strong-interaction data across the\nperiodic table. The value thus derived, $\\sigma_{\\pi N}^{\\rm FG}=57\\pm 7$ MeV,\nis directly connected via the Gell-Mann--Oakes--Renner expression to the\nmedium-renormalized $\\pi N$ isovector scattering amplitude near threshold. It\ncompares well with the value derived recently by the Bern-Bonn-J\\\"{u}lich\ngroup, $\\sigma_{\\pi N}^{\\rm RS}=58\\pm 5$ MeV, using the Roy-Steiner equations\nto control the extrapolation of the vanishingly small near threshold $\\pi N$\nisoscalar scattering amplitude to zero pion mass.", "category": "nucl-th" }, { "text": "Nuclear multifragmentation within the framework of different statistical\n ensembles: The sensitivity of the Statistical Multifragmentation Model to the underlying\nstatistical assumptions is investigated. We concentrate on its micro-canonical,\ncanonical, and isobaric formulations. As far as average values are concerned,\nour results reveal that all the ensembles make very similar predictions, as\nlong as the relevant macroscopic variables (such as temperature, excitation\nenergy and breakup volume) are the same in all statistical ensembles. It also\nturns out that the multiplicity dependence of the breakup volume in the\nmicro-canonical version of the model mimics a system at (approximately)\nconstant pressure, at least in the plateau region of the caloric curve.\nHowever, in contrast to average values, our results suggest that the\ndistributions of physical observables are quite sensitive to the statistical\nassumptions. This finding may help deciding which hypothesis corresponds to the\nbest picture for the freeze-out stage", "category": "nucl-th" }, { "text": "The nuclear configurational entropy approach to dynamical QCD effects: This paper scrutinizes the dynamical QCD effects influence on mesons, namely,\nthe mean-square root radius of a pion in the holographic light-front wave\nfunction setup, in the context of the AdS/QCD. The nuclear configurational\nentropy, associated to mesonic holographic light-front wave functions, is shown\nto have a critical point that optimizes the two parameters of the spin-improved\nlight-front wave function. The mean-square root pion radius and its\ncross-section, computed upon these derived values, match the exact existing\nexperimental data to the precision of 0.14\\%, below the experimental error at\nthe PDG.", "category": "nucl-th" }, { "text": "Energy dependence of heavy-ion initial condition in isobar collisions: Collisions of isobar nuclei, those with the same mass number but different\nstructure parameters, provide a new way to probe the initial condition of the\nheavy ion collisions. Using transport model simulation of $^{96}$Ru+$^{96}$Ru\nand $^{96}$Zr+$^{96}$Zr collisions at two energies $\\sqrt{s_{\\mathrm{NN}}}=0.2$\nTeV and 5.02 TeV, where $^{96}$Ru and $^{96}$Zr nuclei have significantly\ndifferent deformations and radial profiles, we identify sources of\neccentricities contributing independently to the final state harmonic flow\n$v_n$. The efficacy for flow generation is different amount these sources,\nwhich qualitatively explains the modest yet significant energy dependence of\nthe isobar ratios of $v_n$. Experimental measurement of these ratios at the LHC\nenergy and compared with those obtained at RHIC will provide useful insight\ninto the collision-energy dependence of the initial condition.", "category": "nucl-th" }, { "text": "Path Integral Quantum Monte Carlo Method for Light Nuclei: I describe the first continuous space nuclear path integral quantum Monte\nCarlo method, and calculate the ground state properties of light nuclei\nincluding Deuteron, Triton, Helium-3 and Helium-4, using both local chiral\ninteraction up to next-to-next-to-leading-order and the Argonne $v_6'$\ninteraction. Compared with diffusion based quantum Monte Carlo methods such as\nGreen's function Monte Carlo and auxiliary field diffusion Monte Carlo, path\nintegral quantum Monte Carlo has the advantage that it can directly calculate\nthe expectation value of operators without tradeoff, whether they commute with\nthe Hamiltonian or not. For operators that commute with the Hamiltonian, e.g.,\nthe Hamiltonian itself, the path integral quantum Monte Carlo light-nuclei\nresults agree with Green's function Monte Carlo and auxiliary field diffusion\nMonte Carlo results. For other operator expectations which are important to\nunderstand nuclear measurements but do not commute with the Hamiltonian and\ntherefore cannot be accurately calculated by diffusion based quantum Monte\nCarlo methods without tradeoff, the path integral quantum Monte Carlo method\ngives reliable results. I show root-mean-square radii, one-particle number\ndensity distributions, and Euclidean response functions for single-nucleon\ncouplings. I also systematically describe all the sampling algorithms used in\nthis work, the strategies to make the computation efficient, the error\nestimations, and the details of the implementation of the code to perform\ncalculations. This work can serve as a benchmark test for future calculations\nof larger nuclei or finite temperature nuclear matter using path integral\nquantum Monte Carlo.", "category": "nucl-th" }, { "text": "The Non-Local Nature of the Nuclear Force and its Impact on Nuclear\n Structure: We calculate the triton binding energy with a non-local NN potential that\nfits the world NN data below 350 MeV with the almost perfect $\\chi^2$/datum of\n1.03. The non-locality is derived from relativistic meson field theory. The\nresult obtained in a 34-channel, charge-dependent Faddeev calculation is 8.00\nMeV, which is 0.4 MeV above the predictions by local NN potentials. The\nincrease in binding energy can be clearly attributed to the off-shell behavior\nof the non-local potential. Our result cuts in half the discrepancy between\ntheory and experiment established from local NN potentials. Implications for\nother areas of microscopic nuclear structure, in which underbinding is a\ntraditional problem, are discussed.", "category": "nucl-th" }, { "text": "Correlation Effects in the Final-State Interaction for Quasielastic\n $(e,e'p)$ Scattering: Color transparency predicts that, in $(e,e'p)$ reactions at large $Q^2$, the\nfinal-state interaction becomes weaker than the reference value predicted from\nthe free-nucleon cross section. This reference value is usually evaluated in\nthe dilute-gas approximation to Glauber's multiple-scattering theory. We derive\nthe leading-order correction taking into account two-body correlations. Large\ncancellations are found so that the overall correlation effect is small.", "category": "nucl-th" }, { "text": "Fusion Hindrance and the Role of Shell Effects in the Superheavy Mass\n Region: We present the first attempt of the systematical investigation about the\neffects of shell correction energy for dynamical processes, which include\nfusion, fusion-fission and quasi-fission processes. In the superheavy mass\nregion, for the fusion process, the shell correction energy plays a very\nimportant role and enhances the fusion probability, when the colliding partner\nhas strong shell structure. By analyzing the trajectory in the\nthree-dimensional coordinate space with a Langevin equation, we reveal the\nmechanism of the enhancement of the fusion probability caused by shell effects.", "category": "nucl-th" }, { "text": "Generalized density functional equation of state for astrophysical\n simulations with 3-body forces and quark gluon plasma: We present an updated general purpose nuclear equation of state (EoS) for use\nin simulations of core-collapse supernovae, neutron star mergers and black hole\ncollapse. This EoS is formulated in the context of Density Functional Theory\n(DFT) and is generalized to include all DFT EoSs consistent with known nuclear\nand astrophysical constraints. This EoS also allows for the possibility of the\nformation of material with a net proton excess ($Y_p > 0.5$) and has an\nimproved treatment of the nuclear statistical equilibrium and the transition to\nheavy nuclei as the density approaches nuclear matter density. We include the\neffects of pions in the regime above nuclear matter density and incorporate all\nof the known mesonic and baryonic states at high temperature.\n We analyze how a 3-body nuclear force term in the DFT at high densities\nstiffens the EoS to satisfy the maximum neutron star constraint, however the\ndensity dependence of the symmetry anergy and the formation of pions at high\ntemperatures allows for a softening of the central core in supernova collapse\ncalculations leading to a robust explosion. We also add the possibility of a\ntransition to a QCD chiral-symmetry-restoration and deconfinement phase at\ndensities above nuclear matter density. This paper details the physics, and\nconstraints on, this new EoS and presents an illustration of its implementation\nin both neutron stars and core-collapse supernova simulations. We present the\nfirst results from core-collapse supernova simulations with this EoS.", "category": "nucl-th" }, { "text": "Three-alpha-cluster structure of the 0^+ states in ^{12}C and the\n effective alpha-alpha interactions: The $0^{+}$ states of $^{12}\\mathrm{C}$ are considered within the framework\nof the microscopic three-$\\alpha$-cluster model. The main attention is paid to\naccurate calculation of the width of the extremely narrow near-threshold\n$0^+_2$ state which plays a key role in stellar nucleosynthesis. It is shown\nthat the $0^{+}_2$-state decays by means of the sequential mechanism\n${^{12}\\mathrm{C}} \\to \\alpha+{^8\\mathrm{Be}} \\to 3\\alpha$. Calculations are\nperformed for a number of effective $\\alpha - \\alpha$ potentials which are\nchosen to reproduce both energy and width of $^8\\mathrm{Be}$. The parameters of\nthe additional three-body potential are chosen to fix both the ground and\nexcited state energies at the experimental values. The dependence of the width\non the parameters of the effective $\\alpha - \\alpha$ potential is studied in\norder to impose restrictions on the potentials.", "category": "nucl-th" }, { "text": "Unifying Nucleon and Quark Dynamics at Finite Baryon Number Density: We present a model of baryonic matter which contains free constituent quarks\nin addition to bound constituent quarks in nucleons. In addition to the common\nlinear sigma-model we include the exchange of vector-mesons. The percentage of\nfree quarks increases with baryon density but the nucleons resist a restoration\nof chiral symmetry.", "category": "nucl-th" }, { "text": "q- Deformed Boson Expansions: A deformed boson mapping of the Marumori type is derived for an underlying\n$su(2)$ algebra. As an example, we bosonize a pairing hamiltonian in a two\nlevel space, for which an exact treatment is possible. Comparisons are then\nmade between the exact result, our q- deformed boson expansion and the usual\nnon - deformed expansion.", "category": "nucl-th" }, { "text": "Proton-Neutron Pairing Amplitude as a Generator Coordinate for\n Double-Beta Decay: We treat proton-neutron pairing amplitudes, in addition to the nuclear\ndeformation, as generator coordinates in a calculation of the neutrinoless\ndouble-beta decay of 76Ge. We work in two oscillator shells, with a Hamiltonian\nthat includes separable terms in the quadrupole, spin-isospin, and pairing\n(isovector and isoscalar) channels. Our approach allows larger single-particle\nspaces than the shell model and includes the important physics of the\nproton-neutron quasiparticle random-phase approximation (QRPA) without\ninstabilities near phase transitions. After comparing the results of a\nsimplified calculation that neglects deformation with those of the QRPA, we\npresent a more realistic calculation with both deformation and proton-neutron\npairing amplitudes as generator coordinates. The future should see\nproton-neutron coordinates used together with energy-density functionals.", "category": "nucl-th" }, { "text": "Self-Consistent Separable Rpa Approach for Skyrme Forces: Axial Nuclei: The self-consistent separable RPA (random phase approximation) method is\nformulated for Skyrme forces with pairing. The method is based on a general\nself-consistent procedure for factorization of the two-body interaction. It is\nrelevant for various density- and current-dependent functionals. The\ncontributions of the time-even and time-odd Skyrme terms as well as of the\nCoulomb and pairing terms to the residual interaction are taken\nself-consistently into account. Most of the expression have a transparent\nanalytical form, which makes the method convenient for the treatment and\nanalysis. The separable character of the residual interaction allows to avoid\ndiagonalization of high-rank RPA matrices and thus to minimize the calculation\neffort. The previous studies have demonstrated high numerical accuracy and\nefficiency of the method for spherical nuclei. In this contribution, the method\nis specified for axial nuclei. We provide systematic and detailed presentation\nof formalism and discuss different aspects of the model.", "category": "nucl-th" }, { "text": "Time-Dependent Hartree-Fock Approach to Nuclear Pasta at Finite\n Temperature: We present simulations of neutron-rich matter at subnuclear densities, like\nsupernova matter, with the time-dependent Hartree-Fock approximation at\ntemperatures of several MeV. The initial state consists of $\\alpha$ particles\nrandomly distributed in space that have a Maxwell-Boltzmann distribution in\nmomentum space. Adding a neutron background initialized with Fermi distributed\nplane waves the calculations reflect a reasonable approximation of\nastrophysical matter. This matter evolves into spherical, rod-like, and\nslab-like shapes and mixtures thereof. The simulations employ a full Skyrme\ninteraction in a periodic three-dimensional grid. By an improved morphological\nanalysis based on Minkowski functionals, all eight pasta shapes can be uniquely\nidentified by the sign of only two valuations, namely the Euler characteristic\nand the integral mean curvature. In addition, we propose the variance in the\ncell density distribution as a measure to distinguish pasta matter from uniform\nmatter.", "category": "nucl-th" }, { "text": "Bimodality - a Sign of Critical Behavior in Nuclear Reactions: The recently discovered coexistence of multifragmentation and residue\nproduction for the same total transverse energy of light charged particles can\nbe well reproduced in numerical simulations of the heavy ion reactions. A\ndetailed analysis shows that fluctuations (introduced by elementary\nnucleon-nucleon collisions) determine which of the exit states is realized.\nThus we observe for the first time nonlinear dynamics in heavy ion reactions.\nAlso the scaling of the coexistence region with beam energy is well reproduced\nin these results from the QMD simulation program.", "category": "nucl-th" }, { "text": "Comparative tests of isospin-symmetry-breaking corrections to\n superallowed 0+-to-0+ nuclear beta decay: We present a test with which to evaluate the calculated\nisospin-symmetry-breaking corrections to superallowed 0+-to-0+ nuclear beta\ndecay. The test is based on the corrected experimental Ft values being required\nto satisfy conservation of the vector current (CVC). When applied to six sets\nof published calculations, the test demonstrates quantitatively that only one\nset -- the one based on the shell model with Saxon-Woods radial wave functions\n-- provides satisfactory agreement with CVC. This test can easily be applied to\nany sets of calculated correction terms that are produced in future.", "category": "nucl-th" }, { "text": "Thermal description of particle production in ultra-relativistic\n heavy-ion collisions: The grand-canonical version of the thermal model is used to analyze the\nratios of particle abundances measured in ultra-relativistic heavy-ion\ncollisions. Exactly the same model is applied to study the heavy-ion reactions\nat BNL AGS, CERN SPS, and BNL RHIC. A very good description is achieved for\nPb+Pb collisions at SPS, and for Au+Au collisions at RHIC. In these two cases\nthe value of the temperature characterizing the chemical freeze-out is\npractically same: T=168 MeV at SPS and T=165 MeV at RHIC. On the other hand,\nthe particle ratios measured in the collisions of lighter nuclei are described\nonly in the qualitative way. We discuss also the effect of the possible\nin-medium modifications of hadron masses and widths on the thermal fits. For\nPb+Pb collisions at SPS and Au+Au collisions at RHIC we find that the chi^2\nfits favor slightly a moderate (20%) decrease of the masses. In-medium\nmodifications of the widths have little effect on the fits, unless they are\nincreased by a factor larger than 2. We study in detail the thermodynamic\nconditions characterizing the chemical freeze-out. In particular, we find that\nthe average baryon energy is 1.6 GeV and the average meson energy is 0.9 GeV.\nThis difference reflects a different behavior of the mass spectra of mesons and\nbaryons.", "category": "nucl-th" }, { "text": "Charge-Exchange Reaction pD->n(pp) in the Bethe-Salpeter Approach: The deuteron charge - exchange reaction pD->n(pp) for the low values of\nmomentum transfer and small excitation energies of final pp - pair is\nconsidered in the framework of Bethe - Salpeter approach. The method of\ncalculation of the observables is developed for the case, when the pp - pair is\nin $^1S_0$ - state. The methodical numerical calculations of the differetial\ncross sections and tensor analysing powers are presented. The reaction under\nconsideration is predicted to be a solid base for construction of the deuteron\ntensor polarimeter at high energies, and also to obtain some additional\ninformation about elementary nucleon - nucleon charge - exchange amplitude.", "category": "nucl-th" }, { "text": "Heavy ion collisions at intermediate energies in a quark-gluon exchange\n framework: Heavy ion collisions at intermediate energies can be studied in the context\nof the Vlasov-Uehling-Uhlenbeck (VUU) model. One of the main features in this\nmodel is the nucleon-nucleon (NN) cross section in the collisional term. Quark\ninterchange plays a role in the NN interaction and its effect can be observed\nin the cross section. We explore the possibility that quark interchange effects\ncan appear in observables at energies lower than RHIC.", "category": "nucl-th" }, { "text": "Probing the resonance of Dirac particle by the application of complex\n momentum representation: Resonance plays critical roles in the formation of many physical phenomena,\nand several methods have been developed for the exploration of resonance. In\nthis work, we propose a new scheme for resonance by solving the Dirac equation\nin complex momentum representation, in which the resonant states are exposed\nclearly in complex momentum plane and the resonance parameters can be\ndetermined precisely without imposing unphysical parameters. Combining with the\nrelativistic mean-field theory, this method is applied to probe the resonances\nin $^{120}$Sn with the energies, widths, and wavefunctions being obtained.\nComparing with other methods, this method is not only very effective for narrow\nresonances, but also can be reliably applied to broad resonances.", "category": "nucl-th" }, { "text": "Pre-equilibrium dynamics and heavy-ion observables: To bracket the importance of the pre-equilibrium stage on relativistic\nheavy-ion collision observables, we compare simulations where it is modeled by\neither free-streaming partons or fluid dynamics. These cases implement the\nassumptions of extremely weak vs. extremely strong coupling in the initial\ncollision stage. Accounting for flow generated in the pre-equilibrium stage, we\nstudy the sensitivity of radial, elliptic and triangular flow on the switching\ntime when the hydrodynamic description becomes valid. Using the hybrid code\niEBE-VISHNU we perform a multi-parameter search, constrained by particle\nratios, integrated elliptic and triangular charged hadron flow, the mean\ntransverse momenta of pions, kaons and protons, and the second moment $\\langle\np_T^2\\rangle$ of the proton transverse momentum spectrum, to identify optimized\nvalues for the switching time $\\tau_s$ from pre-equilibrium to hydrodynamics,\nthe specific shear viscosity $\\eta/s$, the normalization factor of the\ntemperature-dependent specific bulk viscosity $(\\zeta/s)(T)$, and the switching\ntemperature $T_\\mathrm{sw}$ from viscous hydrodynamics to the hadron cascade\nUrQMD. With the optimized parameters, we predict and compare with experiment\nthe $p_T$-distributions of $\\pi$, $K$, $p$, $\\Lambda$, $\\Xi$ and $\\Omega$\nyields and their elliptic flow coefficients, focusing specifically on the\nmass-ordering of the elliptic flow for protons and Lambda hyperons which is\nincorrectly described by VISHNU without pre-equilibrium flow.", "category": "nucl-th" }, { "text": "Bottomonium production in pp and heavy-ion collisions: We study bottomonium $b\\bar b$ production in pp collisions as well as in\nheavy-ion collisions, using a quantal density matrix approach. The initial\nbottom (anti)quarks are provided by the PYTHIA event generator. We solve the\nSchr\\\"odinger equation for the $b\\bar b$ pair, identifying the potential with\nthe free energy, calculated with lattice QCD, to obtain the temperature\ndependent $b\\bar b$ density matrix as well as the dissociation temperature. The\nformation of bottomonium is given by projection of the bottomonium density\nmatrix onto the density matrix of the system. With this approach we describe\nthe rapidity and transverse momentum distribution of the $\\Upsilon $(nS) in pp\ncollisions at $\\sqrt{s_{\\rm NN}}=$ 5.02 TeV extending a similar calculation for\nthe charmonium states \\cite{Song:2017phm}. We employ the Remler formalism to\nstudy the $b\\bar b$ production in heavy ion collisions in which the heavy\nquarks scatter elastically with partons from the quark gluon plasma (QGP). The\nelastic scattering of heavy (anti)quark in QGP is realized by the dynamical\nquasi-particle model (DQPM) and the expanding QGP is modeled by PHSD. We find\nthat a reduction to 10 \\% of the scattering cross section for a (anti)bottom\nquark with a QGP parton reproduces the experimental data. This suggests that\ndue to color neutrality the scattering cross section of the small $b\\bar b$\nsystem with a parton is considerably smaller than twice the bottom-parton\nscattering cross section.", "category": "nucl-th" }, { "text": "Self-energy Effects in the Superfluidity of Neutron Matter: The superfluidity of neutron matter in the channel $^1 S_0$ is studied by\ntaking into account the effect of the ground-state correlations in the\nself-energy. To this purpose the gap equation has been solved within the\ngeneralized Gorkov approach. A sizeable suppression of the energy gap is driven\nby the quasi-particle strength around the Fermi surface.", "category": "nucl-th" }, { "text": "Exactly solvable Richardson-Gaudin models for many-body quantum systems: The use of exactly-solvable Richardson-Gaudin (R-G) models to describe the\nphysics of systems with strong pair correlations is reviewed. We begin with a\nbrief discussion of Richardson's early work, which demonstrated the exact\nsolvability of the pure pairing model, and then show how that work has evolved\nrecently into a much richer class of exactly-solvable models. We then show how\nthe Richardson solution leads naturally to an exact analogy between such\nquantum models and classical electrostatic problems in two dimensions. This is\nthen used to demonstrate formally how BCS theory emerges as the large-N limit\nof the pure pairing Hamiltonian and is followed by several applications to\nproblems of relevance to condensed matter physics, nuclear physics and the\nphysics of confined systems. Some of the interesting effects that are discussed\nin the context of these exactly-solvable models include: (1) the crossover from\nsuperconductivity to a fluctuation-dominated regime in small metallic grains,\n(2) the role of the nucleon Pauli principle in suppressing the effects of high\nspin bosons in interacting boson models of nuclei, and (3) the possibility of\nfragmentation in confined boson systems. Interesting insight is also provided\ninto the origin of the superconducting phase transition both in two-dimensional\nelectronic systems and in atomic nuclei, based on the electrostatic image of\nthe corresponding exactly-solvable quantum pairing models.", "category": "nucl-th" }, { "text": "Isoscalar M1 and E2 Amplitudes in n+p -> d+gamma: The low energy radiative capture process n+p -> d+gamma provides a sensitive\nprobe of the two-nucleon system. The cross section for this process is\ndominated by the isovector M1 amplitude for capture from the 1S0 channel via\nthe isovector magnetic moment of the nucleon. In this work we use effective\nfield theory to compute the isoscalar M1 and isoscalar E2 amplitudes that are\nstrongly suppressed for cold neutron capture. The actual value of the isoscalar\nE2 amplitude is expected to be within 15% of the value computed in this work.\nIn contrast, due to the vanishing contribution of the one-body operator at\nleading order and next-to-leading order, the isoscalar M1 amplitude is\nestimated to have a large uncertainty. We discuss in detail the deuteron\nquadrupole form factor and SD mixing.", "category": "nucl-th" }, { "text": "Axial vector diquark correlations in the nucleon: Structure functions\n and static properties: In order to extract information on the strength of quark-quark correlations\nin the axial vector (a.v.) diquark channel ($J^P=1^+, T=1$), we analyze the\nquark light cone momentum distributions in the nucleon, in particular their\nflavor dependencies, and the static properties of the nucleon. To construct the\nnucleon as a relativistic 3-quark bound state, we use a simple 'static'\napproximation to the full Faddeev equation in the Nambu-Jona-Lasinio model,\nincluding correlations in the scalar ($J^P=0^+, T=0$) and a.v. diquark\nchannels. It is shown that the a.v. diquark correlations should be rather weak\ncompared to the scalar ones. From our analysis we extract information on the\nstrength of the correlations as well as on the probability of the a.v. diquark\nchannel.", "category": "nucl-th" }, { "text": "Impact of the neutron-star deformability on equation of state parameters: We use a Bayesian inference analysis to explore the sensitivity of Taylor\nexpansion parameters of the nuclear equation of state (EOS) to the neutron star\ndimensionless tidal deformability ($\\Lambda$) on 1 to 2 solar masses neutron\nstars. A global power law dependence between tidal deformability and\ncompactness parameter (M/R) is verified over this mass region. To avoid\nsuperfluous correlations between the expansion parameters, we use a\ncorrelation-free EOS model based on a recently published meta-modeling\napproach. We find that assumptions in the prior distribution strongly influence\nthe constraints on $\\Lambda$. The $\\Lambda$ constraints obtained from the\nneutron star merger event GW170817 prefer low values of $L_\\text{sym}$ and\n$K_\\text{sym}$, for a canonical neutron star with 1.4 solar mass. For neutron\nstar with mass $<1.6$ solar mass, $L_\\text{sym}$ and $K_\\text{sym}$ are highly\ncorrelated with the tidal deformability. For more massive neutron stars, the\ntidal deformability is more strongly correlated with higher order Taylor\nexpansion parameters.", "category": "nucl-th" }, { "text": "On the quark mass dependence of nucleon-nucleon S-wave scattering\n lengths: In the framework of a Chiral effective theory with dibaryon fields, we\ncalculate the pion mass dependence of the inverse scattering length of the\nnucleon-nucleon system in the $^3S_1$ channel at order ${(m_\\pi^3 /\n\\Lambda_\\chi^2)}\\times (m_\\pi^{1/2}m_N^{3/2}/8\\pi f_\\pi^2)^n$ for all $n\\ge 0$.\nWe show that certain sets of potentially large higher order contributions\nvanish. We discuss the difficulties of extending the proof to the $^1S_0$\nchannel. We apply our results to chiral extrapolations of current lattice data.", "category": "nucl-th" }, { "text": "Low energy proton reactions of astrophysical interest in A$\\sim90-100$\n region: Semimicroscopic optical potentials for low energy proton reactions in mass\n90-100 region have been obtained by folding the density dependent M3Y\ninteraction with relativistic mean field densities. Certain parameters in the\npotential have been deduced by comparing calculated results with the data for\nelastic scattering. Low energy proton reactions in this mass region have been\nstudied in the formalism with success. Rates of important astrophysical\nreaction in the mass region have been calculated.", "category": "nucl-th" }, { "text": "Perturbative approaches in relativistic kinetic theory and the emergence\n of first-order hydrodynamics: Hydrodynamics can be formulated in terms of a perturbative series in\nderivatives of the temperature, chemical potential, and flow velocity around an\nequilibrium state. Different formulations for this series have been proposed\nover the years, which consequently led to the development of various\nhydrodynamic theories. In this work, we discuss the relativistic\ngeneralizations of the perturbative expansions put forward by Chapman and\nEnskog, and Hilbert, using general matching conditions in kinetic theory. This\nallows us to describe, in a comprehensive way, how different out-of-equilibrium\ndefinitions for the hydrodynamic fields affect the development of the\nhydrodynamic perturbative series. We provide a perturbative method for\nsystematically deriving the hydrodynamic formulation recently proposed by\nBemfica, Disconzi, Noronha, and Kovtun (BDNK) from relativistic kinetic theory.\nThe various transport coefficients that appear in BDNK (at first-order) are\nexplicitly computed using a new formulation of the relaxation time\napproximation for the Boltzmann equation. Assuming Bjorken flow, we also\ndetermine the hydrodynamic attractors of BDNK theory and compare the overall\nhydrodynamic evolution obtained using this formulation with that generated by\nthe Israel-Stewart equations of motion and also kinetic theory.", "category": "nucl-th" }, { "text": "Nuclear constraints on gravitational waves from deformed pulsars: The recent direct detection of gravitational waves (GWs) from binary black\nhole mergers (2016, Phys. Rev. Lett. 116, no. 6, 061102; no. 24, 241103) opens\nup an entirely new non-electromagnetic window into the Universe making it\npossible to probe physics that has been hidden or dark to electromagnetic\nobservations. In addition to cataclysmic events involving black holes, GWs can\nbe triggered by physical processes and systems involving neutron stars.\nProperties of neutron stars are largely determined by the equation of state\n(EOS) of neutron-rich matter, which is the major ingredient in calculating the\nstellar structure and properties of related phenomena, such as gravitational\nwave emission from elliptically deformed pulsars and neutron star binaries.\nAlthough the EOS of neutron-rich matter is still rather uncertain mainly due to\nthe poorly known density dependence of nuclear symmetry energy at high\ndensities, significant progress has been made recently in constraining the\nsymmetry energy using data from terrestrial nuclear laboratories. These\nconstraints could provide useful information on the limits of GWs expected from\nneutron stars. Here after briefly reviewing our previous work on constraining\ngravitational radiation from elliptically deformed pulsars with terrestrial\nnuclear laboratory data in light of the recent gravitational wave detection, we\nestimate the maximum gravitational wave strain amplitude, using an optimistic\nvalue for the breaking strain of the neutron star crust, for 15 pulsars at\ndistances 0.16 kpc to 0.91 kpc from Earth, and find it to be in the range of\n$\\sim[0.2-31.1]\\times 10^{-24}$, depending on the details of the EOS used to\ncompute the neutron star properties. Implications are discussed.", "category": "nucl-th" }, { "text": "Isospin dependent kaon and antikaon optical potentials in dense hadronic\n matter: Isospin effects on the optical potentials of kaons and antikaons in dense\nhadronic matter are investigated using a chiral SU(3) model. These effects are\nimportant for asymmetric heavy ion collision experiments. In the present work\nthe dispersion relations are derived for kaons and antikaons, compatible with\nthe low energy scattering data, within our model approach. The relations result\nfrom the kaonic interactions with the nucleons, vector mesons and scalar mesons\nin the asymmetric nuclear matter. The isospin asymmetry effects arising from\nthe interactions with the vector-isovector $\\rho$- meson as well as the scalar\nisovector $\\delta$ mesons are considered. The density dependence of the isospin\nasymmetry is seen to be appreciable for the kaon and antikaon optical\npotentials. This can be particularly relevant for the future accelerator\nfacility FAIR at GSI, where experiments using neutron rich beams are planned to\nbe used in the study of compressed baryonic matter.", "category": "nucl-th" }, { "text": "Effets de structure dans la diffusion des ions lourds: Nous avons analyse les distributions angulaires de la diffusion elastique\npour differents systemes a des energies proches de la barriere de Coulomb au\nmoyen d'un potentiel semi phenomenologique. Les distributions radiales\ncalculees au moyen de ces potentiels montrent sans ambiguite qu'aux energies\nproches de la barriere de Coulomb, l'absorption se produit dans un etroit\ndomaine de distances de la surface du potentiel nucleaire. Utilisant une\nmodelisation simple de la theorie de Feshbach du potentiel optique, nous avons\ncalcule la contribution a l'absorption due a un nombre reduit d'etats\ncollectifs de surface facilement excitables. L'inclusion d'un terme\nd'absorption phenomenologique pour decrire des processus plus peripheriques que\nles excitations inelastiques, nous a permis de reproduire de maniere\nsatisfaisante les distributions angulaires experimentales de la diffusion\nelastique. Aux plus hautes energies (793 MeV et 1503 MeV), et pour le systeme\n16O+208Pb, nous avons utilise un potentiel reel obtenu moyennant une\nmodelisation simple de la relation de dispersion et nous avons fait usage du\nmodele de fermeture propose par N. Vinh Mau pour calculer le terme d'absorption\ndu potentiel. Nos calculs a 793 MeV conduisent a des resultats identiques a\nceux obtenus avec les potentiels de reference. Par contre a 1503 MeV, les\ncalculs ne reproduisent pas convenablement les donnees experimentales indiquant\nqu'a cette energie l'absorption n'est plus controlee par les seuls processus\ncollectifs.", "category": "nucl-th" }, { "text": "Core-excitation effects in three-body breakup reactions studied using\n the Faddeev formalism: Previous studies of $(d,p)$ reactions in three-body (proton, neutron, nuclear\ncore) systems revealed a nontrivial effect of the core excitation: the transfer\ncross section cannot be factorized into the spectroscopic factor and the\nsingle-particle cross section obtained neglecting the core excitation. This\nobservable, up to a kinematic factor, is the angular distribution of the core\nnucleus in the $(p,d)$ reaction. The study of the core excitation effect for\nthe most closely related observable in the $(p,pn)$ three-body breakup, i.e.,\nthe core angular distribution, is aimed in the present work. Breakup of the\none-neutron halo nucleus in the collision with the proton is described using\nthree-body Faddeev-type equations extended to include the excitation of the\nnuclear core. The integral equations for transition operators are solved in the\nmomentum-space partial-wave representation. Breakup of 11Be nucleus as well as\nof model $A=11$ $p$-wave nuclei is studied at beam energies of 30, 60, and 200\nMeV per nucleon. Angular and momentum distributions for the 10Be core in ground\nand excited states is calculated. In sharp contrast to $(p,d)$ reactions, the\ndifferential cross section in most cases factorizes quite well into the\nspectroscopic factor and the single-particle cross section. Due to different\nreaction mechanisms the core excitation effect in the breakup is very different\nfrom transfer reactions. A commonly accepted approach to evaluate the cross\nsection, i.e., the rescaling of single-particle model results by the\ncorresponding spectroscopic factor, appears to be reliable for breakup though\nit fails in general for transfer reactions.", "category": "nucl-th" }, { "text": "Modeling Cluster Production at the AGS: Deuteron coalescence, during relativistic nucleus-nucleus collisions, is\ncarried out in a model incorporating a minimal quantal treatment of the\nformation of the cluster from its individual nucleons by evaluating the overlap\nof intial cascading nucleon wave packets with the final deuteron wave function.\nIn one approach the nucleon and deuteron center of mass wave packet sizes are\nestimated dynamically for each coalescing pair using its past light-cone\nhistory in the underlying cascade, a procedure which yields a parameter free\ndetermination of the cluster yield. A modified version employing a global\nestimate of the deuteron formation probability, is identical to a general\nimplementation of the Wigner function formalism but can differ from the most\nfrequent realisation of the latter. Comparison is made both with the extensive\nexisting E802 data for Si+Au at 14.6 GeV/c and with the Wigner formalism. A\nglobally consistent picture of the Si+Au measurements is achieved. In light of\nthe deuteron's evident fragility, information obtained from this analysis may\nbe useful in establishing freeze-out volumes and help in heralding the presence\nof high-density phenomena in a baryon-rich environment.", "category": "nucl-th" }, { "text": "Validity of the one-body current for the calculation of form factors in\n the point form of relativistic quantum mechanics: Form factors are calculated in the point form of relativistic quantum\nmechanics for the lowest energy states of a system made of two scalar particles\ninteracting via the exchange of a massless boson. They are compared to the\nexact results obtained by using solutions of the Bethe-Salpeter equation which\nare well known in this case (Wick-Cutkosky model). Deficiencies of the\npoint-form approach together with the single-particle current are emphasised.\nThey point to the contribution of two-body currents which are required in any\ncase to fulfil current conservation.", "category": "nucl-th" }, { "text": "Latest results from lattice QCD for the Roper resonance: The present status of the Roper resonance in lattice QCD is reviewed. Some of\nthe latest lattice results are discussed with particular emphasis on a large\nsystematic error stemming from the finite size effect. These results suggest\nthat the Roper resonance can be described by the simple three quark excitation\nof sizable extent.", "category": "nucl-th" }, { "text": "Complete inclusion of parity-dependent level densities in the\n statistical description of astrophysical reaction rates: Microscopic calculations show a strong parity dependence of the nuclear level\ndensity at low excitation energy of a nucleus. Previously, this dependence has\neither been neglected or only implemented in the initial and final channels of\nHauser-Feshbach calculations. We present an indirect way to account for a full\nparity dependence in all steps of a reaction, including the one of the compound\nnucleus formed in a reaction. To illustrate the impact on astrophysical\nreaction rates, we present rates for neutron captures in isotopic chains of Ni\nand Sn. Comparing with the standard assumption of equipartition of both\nparities, we find noticeable differences in the energy regime of astrophysical\ninterest caused by the parity dependence of the nuclear level density found in\nthe compound nucleus even at sizeable excitation energies.", "category": "nucl-th" }, { "text": "Scaling within the Spectral Function approach: Scaling features of the nuclear electromagnetic response functions unveil\naspects of nuclear dynamics that are crucial for interpretating neutrino- and\nelectron-scattering data. In the large momentum-transfer regime, the\nnucleon-density response function defines a universal scaling function, which\nis independent of the nature of the probe. In this work, we analyze the\nnucleon-density response function of $^{12}$C, neglecting collective\nexcitations. We employ particle and hole spectral functions obtained within two\ndistinct many-body methods, both widely used to describe electroweak reactions\nin nuclei. We show that the two approaches provide compatible nucleon-density\nscaling functions that for large momentum transfers satisfy first-kind scaling.\nBoth methods yield scaling functions characterized by an asymmetric shape,\nalthough less pronounced than that of experimental scaling functions. This\nasymmetry, only mildly affected by final state interactions, is mostly due to\nnucleon-nucleon correlations, encoded in the continuum component of the hole\nSF.", "category": "nucl-th" }, { "text": "Algebraic treatment of the hyper-Coulomb problem: A completely algebraic treatment of the six-dimensional hypercoulomb problem\nis discussed in terms of an oscillator realization of the dynamical algebra of\nSO(7,2). Closed expressions are derived for the energy spectrum and form\nfactors.", "category": "nucl-th" }, { "text": "Correlated $\\bbox{\u03c0\u03c1}$ Exchange in the $\\bbox{NN}$ Interaction: We evaluate the contribution to the nucleon-nucleon interaction due to\ncorrelated $\\pi\\rho$ exchange in the $\\pi$, $\\omega$, and $A_1$/$H_1$ channels\nby means of dispersion-theoretic methods based on a realistic meson exchange\nmodel for the interaction between $\\pi$ and $\\rho$ mesons. These processes have\nsubstantial effects: In the pionic channel it counterbalances the suppression\ngenerated by a soft $\\pi NN$ form factor of monopole type with a cutoff mass of\nabout 1 GeV; in the $\\omega$-channel it provides nearly half of the empirical\nrepulsion, leaving little room for explicit quark-gluon effects.", "category": "nucl-th" }, { "text": "${\\bar\u039b}/{\\bar p}$ ratios in heavy ion collisions at 11.6 AGeV/c: We attempt to explain the ${\\bar \\Lambda}/\\bar p$ ratios measured in heavy\nion collisions at $11.6~{\\rm A\\cdot GeV}/c$ beam momentum within a hadronic\nframework. This ratio is enhanced relative to corresponding ratios in $pp$\ncollisions, and is large when compared with thermal fits to heavy ion data.\nUsing a detailed cascade calculation, we show that different annihilation\ncross--sections of $\\bar \\Lambda$'s and $\\bar p$'s, and the net conversion of\n$\\bar p$'s to $\\bar \\Lambda$'s, do not account for the enhancement in central\ncollisions. For larger impact parameters, however, hadronic mechanisms may well\nsuffice to produce the observed enhancement. Uncertainties in elementary\ncross--sections and formation times are considered.", "category": "nucl-th" }, { "text": "Parity-Dependence in the Nuclear Level Density: Astrophysical reaction rates are sensitive to the parity distribution at low\nexcitation energies. We combine a formula for the energy-dependent parity\ndistribution with a microscopic-macroscopic nuclear level density. This\napproach describes well the transition from low excitation energies, where a\nsingle parity dominates, to high excitations where the two densities are equal.", "category": "nucl-th" }, { "text": "$\\bar K^*$ meson in dense matter: We study the properties of $\\bar K^*$ mesons in nuclear matter using a\nunitary approach in coupled channels within the framework of the local hidden\ngauge formalism and incorporating the $\\bar K \\pi$ decay channel in matter. The\nin-medium $\\bar K^* N$ interaction accounts for Pauli blocking effects and\nincorporates the $\\bar K^*$ self-energy in a self-consistent manner. We also\nobtain the $\\bar K^*$ (off-shell) spectral function and analyze its behaviour\nat finite density and momentum. At normal nuclear matter density, the $\\bar\nK^*$ meson feels a moderately attractive potential while the $\\bar K^*$ width\nbecomes five times larger than in free space. We estimate the transparency\nratio of the $\\gamma A \\to K^+ K^{* -} A^\\prime$ reaction, which we propose as\na feasible scenario at present facilities to detect the changes of the\nproperties of the $\\bar K^*$ meson in the nuclear medium.", "category": "nucl-th" }, { "text": "Asymmetry in the neutrino and anti-neutrino reactions in a nuclear\n medium: We study the effect of the density-dependent axial and vector form factors on\nthe electro-neutrino ($\\nu_e$) and anti-neutrino $({\\bar \\nu}_e)$ reactions for\na nucleon in nuclear matter or in $^{12}$C. The nucleon form factors in free\nspace are presumed to be modified for a bound nucleon in a nuclear medium. We\nadopt the density-dependent form factors calculated by the quark-meson coupling\n(QMC) model, and apply them to the $\\nu_e$ and ${\\bar \\nu}_e$ induced reactions\nwith the initial energy $E = $ 8 $\\sim$ 80 MeV. We find that the total\n${\\nu}_e$ cross sections on $^{12}$C as well as a nucleon in nuclear matter are\nreduced by about 5% at the nuclear saturation density, $\\rho_0$. This reduction\nis caused by the modification of the nucleon structure in matter. Although the\ndensity effect for both cases is relatively small, it is comparable with the\neffect of Coulomb distortion on the outgoing lepton in the $\\nu$-reaction. In\ncontrast, the density effect on the ${\\bar \\nu}_e$ reaction reduces the cross\nsection significantly in both nuclear matter and $^{12}$C cases, and the amount\nmaximally becomes of about 35% around $\\rho_0$. Such large asymmetry in the\n$\\nu_e$ and ${\\bar \\nu}_e$ cross sections, which seems to be nearly independent\nof the target, is originated from the difference in the helicities of ${\\bar\n\\nu}_e$ and ${\\nu}_e$. It is expected that the asymmetry influences the\nr-process and also the neutrino-process nucleosynthesis in core-collapse\nsupernovae.", "category": "nucl-th" }, { "text": "Mean Field Effect on J/\u03c8Production in Heavy Ion Collisions: The mean field effect in quark-gluon plasma on J/\\psi production in heavy ion\ncollisions is perturbatively calculated in a transport approach. While the\nglobal nuclear modification factor R_{AA} is not sensitive to the mean field,\nthe reduced threshold for J/\\psi regeneration leads to a significant\nenhancement of R_{AA} at low transverse momentum at RHIC and LHC energies.", "category": "nucl-th" }, { "text": "Comparison of GiBUU calculations with MiniBooNE pion production data: Background. Neutrino-induced pion production can give important informationon\nthe axial coupling to nucleon resonances. Furthermore, pion production\nrepresents a major background to quasielastic-like events. Single pion\nproduction data from the MiniBooNE in charged current neutrino scattering in\nmineral oil appeared higher than expected within conventional theoretical\napproaches.\n Purpose. We aim to investigate which model parameters affect the calculated\ncross section and how they do this.\n Method. The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used for\nan investigation of neutrino-nucleus reactions.\n Results. Presented are integrated and differential cross sections for 1\\pi^+\nand 1\\pi^0 production before and after final state interactions in comparison\nwith the MiniBooNE data.\n Conclusions. For the MiniBooNE flux all processes (QE, 1\\pi-background,\n\\Delta, higher resonance production, DIS) contribute to the observed final\nstate with one pion of a given charge. The uncertainty in elementary pion\nproduction cross sections leads to a corresponding uncertainty in the nuclear\ncross sections. Final state interactions change the shape of the muon-related\nobservables only slightly, but they significantly change the shape of pion\ndistributions.", "category": "nucl-th" }, { "text": "A theoretical approach to study J/$\u03a8$ suppression in relativistic\n heavy ion collisions: With a view to understanding J/$\\Psi$ suppression in relativistic heavy ion\ncollisions, we compute the suppression rate within the framework of\nhydrodynamical evolution model. For this, we consider an ellipsoidal flow and\nuse an ansatz for temperature profile function which accounts for time and the\nthree dimensional space evolution of the quark-gluon plasma. We have calculated\nthe survival probability separately as the function of transverse and\nlongitudinal momentum. We have shown that previous calculations are special\ncases of this model.", "category": "nucl-th" }, { "text": "Separability of a Low-Momentum Effective Nucleon-Nucleon Potential: A realistic nucleon-nucleon potential is transformed into a low-momentum\neffective one (LMNN) using the Okubo theory. The separable potentials are\nconverted from the LMNN with a universal separable expansion method and a\nsimple Legendre expansion. Through the calculation of the triton binding\nenergies, the separability for the convergence of these ranks is evaluated. It\nis found that there is a tendency for the lower momentum cutoff parameter\n$\\Lambda$ of LMNN to gain good separability.", "category": "nucl-th" }, { "text": "Hydrodynamic fluctuations and two-point correlations: We examine correlations of energy density induced by initial state\nfluctuations, which are localized in both transverse and longitudinal extent.\nThe hotspots are evolved according to hydrodynamics in a background which\nincludes radial flow. Two-point energy density correlations from these hotspots\nare computed as a function of the difference in azimuthal angle and rapidity.\nSuch localized perturbations occur naturally in the theory of hydrodynamic\nfluctuations and may provide insight into some features of the two-particle\ncorrelation data from RHIC and the LHC.", "category": "nucl-th" }, { "text": "Superfluid neutron matter in the s-channel exchange nucleon-nucleon\n interaction models: The superfluid pairing gap of neutron matter is calculated in the framework\nof Quark Compound Bag model with nucleon-nucleon interactions generated by the\ns-channel exchange of Jaffe-Low primitives (6-quark states).", "category": "nucl-th" }, { "text": "Quasinormal modes of scalar field coupled to Einstein's tensor in the\n non-commutative geometry inspired black hole: We investigate the quasinormal modes (QNMs) of the scalar field coupled to\nthe Einstein's tensor in the non-commutative geometry inspired black hole\nspacetime. It is found that the lapse function of the non-commutative black\nhole metric can be represented by a Kummer's confluent hypergeometric function,\nwhich can effectively solve the problem that the numerical results of the QNMs\nare sensitive to the model parameters and make the QNMs values more reliable.\nWe make a careful analysis of the scalar QNM frequencies by using several\nnumerical methods, and find that the numerical results obtained by the new WKB\nmethod (the Pad\\'e approximants) and the Mashhoon method\n(P$\\ddot{\\text{o}}$schl-Teller potential method) are quite different from those\nobtained by the asymptotic iterative method (AIM) and time-domain integration\nmethod when the non-commutative parameter $\\theta$ and coupling parameter\n$\\eta$ are large. The most obvious difference is that the numerical results\nobtained by the AIM and the time-domain integration method appear a critical\nvalue $\\eta_c$ with an increase of $\\eta$, which leads to the dynamical\ninstability. After carefully analyzing the numeral results, we conclude that\nthe numerical results obtained by the AIM and the time-domain integration\nmethod are closer to the theoretical values than those obtained by the WKB\nmethod and the Mashhoon method, when the $\\theta$ and $\\eta$ are large.\nMoreover, through a numerical fitting, we obtain that the functional\nrelationship between the threshold $\\eta_c$ and the non-commutative parameter\n$\\theta$ satisfies $\\eta_{c}=a\\theta^{b}+c$ for a fixed $l$ approximately. We\nfind that the stability of dynamics can be ensured in the $\\eta<\\eta_c(\\theta,\nl)$ region.", "category": "nucl-th" }, { "text": "Flow Coefficients and Jet Characteristics in Heavy Ion Collisions: Identifying jets in heavy ion collisions is of significant interest since the\nproperties of jets are expected to get modified because of the formation of\nquark gluon plasma. The detection of jets is, however, difficult because of\nlarge number of non-jet hadrons produced in the collision process. In this work\nwe propose a method of identifying a jet and determining its transverse\nmomentum by means of flow analysis. This has been done an event-by-event basis.", "category": "nucl-th" }, { "text": "Hadron Physics from the Global Color Model of QCD: We review recent progress in modeling the quark-gluon content of mesons and\ntheir low-energy interactions through the Global Color Model field theory. An\nemphasis is placed on techniques that are shared with the approach based on\ntruncations of the Dyson-Schwinger equations of QCD. In contrast to most other\nfield theory models for QCD degrees of freedom in hadron physics, this approach\ndirectly deals with the derived intrinsic space-time extent of the meson modes\nin their role as field variables and can accommodate confinement as well as\ndynamical breaking of chiral symmetry. Various theoretical techniques and\napproximations found useful in this approach are described. Selected\napplications reviewed here include the properties and interactions of the\nGoldstone bosons, interaction vertex functions, low energy chiral observables,\nelectromagnetic interactions and form factors, and transition form factors.\nSome initial considerations of Vector Meson Dominance and pion loop processes\nare discussed.", "category": "nucl-th" }, { "text": "Surface-integral formalism of deuteron stripping: The purpose of this paper is to develop an alternative theory of deuteron\nstripping to resonance states based on the surface integral formalism of\nKadyrov et al. [Ann. Phys. 324, 1516 (2009)] and continuum-discretized coupled\nchannels (CDCC).\n First we demonstrate how the surface integral formalism works in the\nthree-body model and then we consider a more realistic problem in which a\ncomposite structure of target nuclei is taken via optical potentials. We\nexplore different choices of channel wave functions and transition operators\nand show that a conventional CDCC volume matrix element can be written in terms\nof a surface-integral matrix element, which is peripheral, and an auxiliary\nmatrix element, which determines the contribution of the nuclear interior over\nthe variable $r_{nA}$. This auxiliary matrix element appears due to the\ninconsistency in treating of the $n-A$ potential: this potential should be real\nin the final state to support bound states or resonance scattering and complex\nin the initial state to describe $n-A$ scattering. Our main result is\nformulation of the theory of the stripping to resonance states using the prior\nform of the surface integral formalism and CDCC method. It is demonstrated that\nthe conventional CDCC volume matrix element coincides with the surface matrix\nelement, which converges for the stripping to the resonance state. Also the\nsurface representation (over the variable $r_{nA}$ of the stripping matrix\nelement enhances the peripheral part of the amplitude although the internal\ncontribution doesn't disappear and increases with increase of the deuteron\nenergy. We present calculations corroborating our findings for both stripping\nto the bound state and the resonance.", "category": "nucl-th" }, { "text": "Spin-tensor decomposition of nuclear transition matrix elements for\n neutrinoless double-$\u03b2$ decay of $^{76}$Ge and $^{82}$Se nuclei within\n PHFB approach: Employing the PHFB model, nuclear transition matrix elements $M^{\\left(\nK\\right) }$ for the neutrinoless double-$\\beta^{-} $ decay of $\\ ^{76}$Ge and\n$^{82}$Se isotopes are calculated within mechanisms involving light as well as\nheavy Majorana neutrinos, and classical Majorons by considering the spin-tensor\ndecomposition of realistic KUO and empirical JUN45 effective two-body\ninteraction. It is noticed that the effects due to the SRC on NTMEs $M^{\\left(\n0\\nu \\right) }$ and $M^{\\left( 0N\\right) }$ due to the exchange of light and\nheavy Majorana neutrinos, respectively, is maximally incorporated by the\ncentral part of the effective two-body interaction, which varies by a small\namount with the inclusion of spin-orbit and tensor components. The maximum\nuncertainty in the average NTMEs $\\overline{M}^{(0\\nu)}$ and\n$\\overline{M}^{(0N)}$ turns out to be about 10\\% and 37\\%, respectively.", "category": "nucl-th" }, { "text": "Specific features and symmetries for magnetic and chiral bands in nuclei: Magnetic and chiral bands have been a hot subject for more than twenty years.\nTherefore, quite large volumes of experimental data as well as theoretical\ndescriptions have been accumulated. Although some of the formalisms are not so\neasy to handle, the results agree impressively well with the data. The\nobjective of this paper is to review the actual status of both experimental and\ntheoretical investigations. Aiming at making this material accessible to a\nlarge variety of readers, including young students and researchers, I gave some\ndetails on the schematic models which are able to unveil the main features of\nchirality in nuclei. Also, since most formalisms use a rigid triaxial rotor for\nthe nuclear system's core, I devoted some space to the semi-classical\ndescription of the rigid triaxial as well as of the tilted triaxial rotor. In\norder to answer the question whether the chiral phenomenon is spread over the\nwhole nuclear chart and whether it is specific only to a certain type of\nnuclei, odd-odd, odd-even or even-even, the current results in the mass regions\nof $A\\sim 60,80,100,130,180,200$ are briefly described for all kinds of\nodd/even-odd/even systems. The chiral geometry is a sufficient condition for a\nsystem of proton-particle, neutron-hole and a triaxial rotor to have the\nelectromagnetic properties of chiral bands. In order to prove that such\ngeometry is not unique for generating magnetic bands with chiral features, I\npresented a mechanism for a new type of chiral bands. One tries to underline\nthe fact that this rapidly developing field is very successful in pushing\nforward nuclear structure studies.", "category": "nucl-th" }, { "text": "Partonic effects on the elliptic flow at relativistic heavy ion\n collisions: The elliptic flow in heavy ion collisions at RHIC is studied in a multiphase\ntransport model. By converting the strings in the high energy density regions\ninto partons, we find that the final elliptic flow is sensitive to the parton\nscattering cross section. To reproduce the large elliptic flow observed in\nAu+Au collisions at $\\sqrt s=130A$ GeV requires a parton scattering cross\nsection of about 6 mb. We also study the dependence of the elliptic flow on the\nparticle multiplicity, transverse momentum, and particle mass.", "category": "nucl-th" }, { "text": "Parity violation and dynamical relativistic effects in $(\\vec{e},e'N)$\n reactions: It is well known that coincidence quasielastic $(\\vec{e},e'N)$ reactions are\nnot appropriate to analyze effects linked to parity violation due the presence\nof the fifth electromagnetic (EM) response $R^{TL'}$. Nevertheless, in this\nwork we develop a fully relativistic approach to be applied to parity-violating\n(PV) quasielastic $(\\vec{e},e'N)$ processes. This is of importance as a\npreliminary step in the subsequent study of inclusive quasielastic PV\n$(\\vec{e},e')$ reactions. Moreover, our present analysis allows us to\ndisentangle effects associated with the off-shell character of nucleons in\nnuclei, gauge ambiguities and the role played by the lower components in the\nnucleon wave functions, i.e., dynamical relativistic effects. This study can\nhelp in getting clear information on PV effects. Particular attention is paid\nto the relativistic plane-wave impulse approximation where the explicit\nexpressions for the PV single-nucleon responses are shown for the first time.", "category": "nucl-th" }, { "text": "Production of multi-strangeness hypernuclei and the YN-interaction: We investigate for the first time the influence of hyperon-nucleon (YN)\ninteraction models on the strangeness dynamics of antiproton- and $\\Xi$-nucleus\ninteractions. Of particular interest is the formation of bound\nmulti-strangeness hypermatter in reactions relevant for \\panda. The main\nfeatures of two well-established microscopic approaches for YN-scattering are\nfirst discussed and their results are then analysed such that they can be\napplied in transport-theoretical simulations. The transport calculations for\nreactions induced by antiproton beams on a primary target including also the\nsecondary cascade beams on a secondary target show a strong sensitivity on the\nunderlying YN-interaction. In particular, we predict the formation of\n$\\Xi$-hypernuclei with an observable sensitivity on the underlying\n$\\Xi$N-interaction. We conclude the importance of our studies for the\nforthcoming research plans at FAIR.", "category": "nucl-th" }, { "text": "Comment on \"Neutron Skin of $^{208}$Pb from Coherent Pion\n Photoproduction\": We argue that the reaction mechanism for the coherent pion production is not\nknown with sufficient accuracy to determine the neutron radius of 208Pb to the\nclaimed precision of 0.03 fm.", "category": "nucl-th" }, { "text": "A microscopic rotational cranking model and its connection to\n conventional cranking and other collective rotational models: A microscopic time-reversal invariant cranking model (MCRM) for nuclear\ncollective rotation about a single axis and its coupling to intrinsic motion is\nderived. The MCRM is derived by transforming the stationary nuclear Schrodinger\nequation using a collective rotation-intrinsic product wavefunction, imposing\nno constraints on the wavefunction and the nucleon coordinates, and using no\nrelative co-ordinates. The derivatives of the collective-rotation angle are\ndefined in terms of a combination of rigid and irrotational collective flows of\nthe nucleons. The collective wavefunction is chosen to be an eigenstate of the\nangular momentum, yielding a MCRM Schrodinger equation for the intrinsic\nwavefunction that contains a cranking Coriolis energy term that is linear in\nthe angular momentum and shear operators, a collective centrifugal energy term,\nand a rotation-fluctuation energy term. In absence of the irrotational-flow\ncomponent and fluctuation energy term, the MCRM equation reduces to that of the\nconventional cranking model (CCRM), but with a dynamic rigid-flow angular\nvelocity and rigid-flow centrifugal-energy term. The expectation of the angular\nmomentum operator, which is the sum of the collective rotation angular momentum\nand the expectation of the angular momentum in the intrinsic state, would\nreduce to that in the CCRM if the collective rotation angular momentum were\nsmall. However, it is shown that, even for the simple case of the anisotropic\nharmonic oscillator mean-field potential in , the collective rotation angular\nmomentum is not small in the current version of the MCRM, and that this problem\nneeds further study. It is also shown that the MCRM Schrodinger equation is\nreducible to the equations of the particle-plus-rotor, phenomenological and\nmicroscopic collective rotation-vibration, and two-fluid semi-classical\ncollective models.", "category": "nucl-th" }, { "text": "Description of electromagnetic and favored $\u03b1$-transitions in heavy\n odd-mass nuclei: We describe electromagnetic and favored \\alpha-transitions to rotational\nbands in odd-mass nuclei built upon a single particle state with angular\nmomentum projection $\\Omega=\\frac{1}{2}$ in the region $88 \\le Z \\le 98$. We\nuse the particle coupled to an even-even core approach described by the\nCoherent State Model (CSM) and the coupled channels method to estimate partial\n$\\alpha$-decay widths. We reproduce the energy levels of the rotational band\nwhere favored $\\alpha$-transitions occur for 26 nuclei and predict B (E2)\nvalues for electromagnetic transitions to the bandhead using a deformation\nparameter and a Hamiltonian strength parameter for each nucleus, together with\nan effective collective charge depending linearly on the deformation parameter.\nWhere experimental data is available, the contribution of the single particle\neffective charge to the total B (E2) value is calculated. The Hamiltonian\ndescribing the $\\alpha$- nucleus interaction contains two terms, a spherically\nsymmetric potential given by the double-folding of the M3Y nucleon-nucleon\ninteraction plus a repulsive core simulating the Pauli principle and a\nquadrupole-quadrupole (QQ) interaction. The $\\alpha$-decaying state is\nidentified as a narrow outgoing resonance in this potential. The intensity of\nthe transition to the first excited state is reproduced by the QQ coupling\nstrength. It depends linearly both on the nuclear deformation and the square of\nthe reduced width for the decay to the bandhead, respectively. Predicted\nintensities for transitions to higher excited states are in a reasonable\nagreement with experimental data. This formalism offers a unified description\nof energy levels, electromagnetic and favored $\\alpha$-transitions for known\nheavy odd-mass $\\alpha$-emitters.", "category": "nucl-th" }, { "text": "Lambda collective flow in heavy ion reactions: Collective flow of Lambda hyperons in heavy ion reactions at SIS energies is\ninvestigated. It is found that a $\\Lambda$ mean field constructed on the basis\nof the quark model leads to a good description of the experimental data of the\nin-plane transverse flow of $\\Lambda$'s. The attractive mean field can also\ngive rise to an additional \"virtual\" $\\Lambda$ radial flow directed inwards,\nwhich is reflected by a \"concave\" structure of the transverse mass spectrum of\nthe $\\Lambda$ hyperons emitted at midrapidity. The $\\Lambda$ radial flow is\nfound to exhibit a strong mass dependence: The flow is visible in the Ni+Ni\nsystem, but is strongly reduced in the system of Au on Au.", "category": "nucl-th" }, { "text": "One-body Langevin dynamics in heavy-ion collisions at intermediate\n energies: We present a new framework to treat the dissipation and fluctuation dynamics\nassociated with nucleon-nucleon scattering in heavy-ion collisions. The\ntwo-body collision processes are effectively described in terms of the\ndiffusion of nucleons in viscous nuclear media, governed by a set of Langevin\nequations in momentum space. The new framework combined with the usual mean\nfield dynamics can be used to simulate heavy-ion collisions at intermediate\nenergies. As a proof of principle, we simulate Au + Au reactions and obtain\nresults consistent with other existing codes under the same constrained\nconditions. We also study the formation of fragments in Sn + Sn reactions at 50\nMeV/nucleon, and results are discussed and compared with two other models\ncommonly employed for collisions.", "category": "nucl-th" }, { "text": "Reaction Operator Approach to Non-Abelian Energy Loss: A systematic expansion of the induced inclusive gluon radiation associated\nwith jet production in a dense QCD plasma is derived using a reaction operator\nformalism. Analytic expressions for the transverse momentum and light-cone\nmomentum distributions are derived to all orders in powers of the gluon opacity\nof the medium, $N\\sigma_g/A=L/\\lambda_g$. The reaction operator approach also\nleads to a simple algebraic proof of the ``color triviality'' of single\ninclusive distributions and to a solvable set of recursion relations. The\nanalytic solution generalizes previous continuum solutions (BDMPS) for\napplications to mesoscopic QCD plasmas. The solution is furthermore not\nrestricted to uncorrelated geometries and allows for evolving screening scales\nas well as the inclusion of finite kinematic constraints. The later is\nparticularly important because below LHC energies the kinematic constraints\nsignificantly decrease the non-abelian energy loss. Our solution for the\ninclusive distribution also generalizes the finite order exclusive (tagged)\ndistribution case studied previously (GLV1). The form of the analytic solution\nis well suited for numerical implementation in Monte Carlo event generators to\nenable more accurate calculations of jet quenching in ultra-relativistic\nnuclear collisions. Numerical results illustrating the constributions of the\nfirst three orders in opacity are compared to the ``self-quenching'' hard\nradiation intensity. A surprising result is that the induced gluon radiation\nintensity is dominated by the (quadratic in $L$) first order opacity\ncontribution for realistic geometries and jet energies in nuclear collisions.", "category": "nucl-th" }, { "text": "Calculation Energy levels and charge radius for odd $^{41-49}$Ca\n Isotopes by using the analytical approach: In the present study, some static properties of odd isotopes of Ca were\ninvestigated in the non-relativistic shell model. We also suggested a novel\nsuitable local potential model for the non-microscopic investigation of the\nmentioned nuclei. We modeled the odd $^{41-49}$Ca nuclei as doubly-magic\nisotopes, with further nucleons (valence) in the lf7/2 and 2p3/2 levels. Then\nthe modified Eckart potential as well as Hulthen potential were chosen for the\ninteraction between core and nucleons. We also used the Parametric Nikiforov\nUvarov method to calculate the values of energy, the radius of charge and wave\nfunction. The obtained results showed a good agreement with the experimental\ndata, so this model is applicable for the similar nuclei.", "category": "nucl-th" }, { "text": "Semiempirical Shell Model Masses with Magic Number Z = 126 for\n Superheavy Elements: A semiempirical shell model mass equation applicable to superheavy elements\nup to Z = 126 is presented and shown to have a high predictive power. The\nequation is applied to the recently discovered superheavy nuclei Z = 118, A =\n293 and Z = 114, A = 289 and their decay products.", "category": "nucl-th" }, { "text": "Collective Hamiltonian for chiral modes: A collective model is proposed to describe the chiral rotation and vibration\nand applied to a system with one $h_{11/2}$ proton particle and one $h_{11/2}$\nneutron hole coupled to a triaxial rigid rotor. The collective Hamiltonian is\nconstructed from the potential energy and mass parameter obtained in the tilted\naxis cranking approach. By diagonalizing the collective Hamiltonian with a box\nboundary condition, it is found that for the chiral rotation, the partner\nstates become more degenerate with the increase of the cranking frequency, and\nfor the chiral vibrations, their important roles for the collective excitation\nare revealed at the beginning of the chiral rotation region.", "category": "nucl-th" }, { "text": "Application of the Kerman-Klein method to the solution of a spherical\n shell model for a deformed rare-earth nucleus: Core-particle coupling models are made viable by assuming that core\nproperties such as matrix elements of multipole and pairing operators and\nexcitation spectra are known independently. From the completeness relation, it\nis seen, however, that these quantities are themselves algebraic functions of\nthe calculated core-particle amplitudes. For the deformed rare-earth nucleus\n158Gd, we find that these sum rules are well-satisfied for the ground state\nband, implying that we have found a self-consistent solution of the non-linear\nKerman-Klein equations.", "category": "nucl-th" }, { "text": "Variational Monte Carlo study of pentaquark states in a correlated quark\n model: Accurate numerical solution of the five-body Schrodinger equation is effected\nvia variational Monte Carlo in a correlated quark model. The spectrum is\nassumed to exhibit a narrow resonance with strangeness S=+1. A fully\nantisymmetrized and pair-correlated five-quark wave function is obtained for\nthe assumed non-relativistic Hamiltonian which has spin, isospin, and color\ndependent pair interactions and many-body confining terms which are fixed by\nthe non-exotic spectra. Gauge field dynamics are modeled via flux tube exchange\nfactors. The energy determined for the ground states with spin-parity 1/2-\n(1/2+) is 2.22 GeV (2.50 GeV). A lower energy negative parity state is\nconsistent with recent lattice results.", "category": "nucl-th" }, { "text": "A unified approach for nucleon knock-out, coherent and incoherent pion\n production in neutrino interactions with nuclei: We present a theory of neutrino interactions with nuclei aimed at the\ndescription of the partial cross-sections, namely quasi-elastic and\nmulti-nucleon emission, coherent and incoherent single pion production. For\nthis purpose, we use the theory of nuclear responses treated in the random\nphase approximation, which allows a unified description of these channels. It\nis particularly suited for the coherent pion production where collective\neffects are important whereas they are moderate in the other channels. We also\nstudy the evolution of the neutrino cross-sections with the mass number from\ncarbon to calcium. We compare our approach to the available neutrino\nexperimental data on carbon. We put a particular emphasis on the multi-nucleon\nchannel, which at present is not easily distinguishable from the quasi-elastic\nevents. This component turns out to be quite relevant for the interpretation of\nexperiments (K2K, MiniBooNE, SciBooNE). It can account in particular for the\nunexpected behavior of the quasi-elastic cross-section.", "category": "nucl-th" }, { "text": "A Study of Charge Radii and Neutron Skin Thickness near Nuclear Drip\n Lines: We studied the charge radius, rms radius and neutron skin thickness $\\Delta\nr_{np}$ in even-even isotopes of Si, S, Ar and Ca and isotones of N =20, 28, 50\nand 82. The $\\Delta r_{np}$ in doubly-magic $^{48}$Ca, $^{68}$Ni,\n$^{120,132}$Sn and $^{208}$Pb nuclei has also been calculated. Theoretical\ncalculations are done with the Hartree-Fock-Bogoliubov theory with the\neffective Skyrme interactions. Calculated theoretical estimates are in good\nagreement with the recently available experimental data. The charge radii for\nSi, S, Ar and Ca isotopes is observed to be minimum at neutron number N =14.\nThe theoretically computed results with UNEDF0 model parameterization of\nfunctional are reasonably reproducing the experimental data for $\\Delta r_{np}$\nin $^{48}$Ca, $^{68}$Ni and $^{120,132}$Sn. The energy density functional of\nUNEDF1 model provides much improved result of $\\Delta r_{np}$ for $^{208}$Pb.", "category": "nucl-th" }, { "text": "Solutions of the Faddeev-Yakubovsky equations for the four nucleons\n scattering states: The Faddeev-Yakubowsky equations in configuration space have been solved for\nthe four nucleon system. The results with an S-wave interaction model in the\nisospin approximation are presented. They concern the bound and scattering\nstates below the first three-body threshold. The elastic phase-shifts for the\nN+NNN reaction in different ($S,T$) channels are given and the corresponding\nlow energy expansions are discussed. Particular attention is payed to the n+t\nelastic cross section. Its resonant structure is well described in terms of a\nsimple NN interaction. First results concerning the S-matrix for the coupled\nN+NNN-NN+NN channels and the strong deuteron-deuteron scattering length are\nobtained.", "category": "nucl-th" }, { "text": "Solution of the Skyrme-Hartree-Fock-Bogolyubov equations in the\n Cartesian deformed harmonic-oscillator basis. (VI) HFODD (v2.38j): a new\n version of the program: We describe the new version (v2.38j) of the code HFODD which solves the\nnuclear Skyrme-Hartree-Fock or Skyrme-Hartree-Fock-Bogolyubov problem by using\nthe Cartesian deformed harmonic-oscillator basis. In the new version, we have\nimplemented: (i) projection on good angular momentum (for the Hartree-Fock\nstates), (ii) calculation of the GCM kernels, (iii) calculation of matrix\nelements of the Yukawa interaction, (iv) the BCS solutions for state-dependent\npairing gaps, (v) the HFB solutions for broken simplex symmetry, (vi)\ncalculation of Bohr deformation parameters, (vii) constraints on the Schiff\nmoments and scalar multipole moments, (viii) the D2h transformations and\nrotations of wave functions, (ix) quasiparticle blocking for the HFB solutions\nin odd and odd-odd nuclei, (x) the Broyden method to accelerate the\nconvergence, (xi) the Lipkin-Nogami method to treat pairing correlations, (xii)\nthe exact Coulomb exchange term, (xiii) several utility options, and we have\ncorrected two insignificant errors.", "category": "nucl-th" }, { "text": "Collective flow and two-pion correlations from a relativistic\n hydrodynamic model with early chemical freeze out: We investigate the effect of early chemical freeze-out on radial flow,\nelliptic flow and HBT radii by using a fully three dimensional hydrodynamic\nmodel. When we take account of the early chemical freeze-out, the space-time\nevolution of temperature in the hadron phase is considerably different from the\nconventional model in which chemical equilibrium is always assumed. As a\nresult, we find that radial and elliptic flows are suppressed and that the\nlifetime and the spatial size of the fluid are reduced. We analyze the p_t\nspectrum, the differential elliptic flow, and the HBT radii at the RHIC energy\nby using hydrodynamics with chemically non-equilibrium equation of state.", "category": "nucl-th" }, { "text": "Two-particle spatial correlations in superfluid nuclei: We discuss the effect of pairing on two-neutron space correlations in\ndeformed nuclei. The spatial correlations are described by the pairing tensor\nin coordinate space calculated in the HFB approach. The calculations are done\nusing the D1S Gogny force. We show that the pairing tensor has a rather small\nextension in the relative coordinate, a feature observed earlier in spherical\nnuclei. It is pointed out that in deformed nuclei the coherence length\ncorresponding to the pairing tensor has a pattern similar to what we have found\npreviously in spherical nuclei, i.e., it is maximal in the interior of the\nnucleus and then it is decreasing rather fast in the surface region where it\nreaches a minimal value of about 2 fm. This minimal value of the coherence\nlength in the surface is essentially determined by the finite size properties\nof single-particle states in the vicinity of the chemical potential and has\nlittle to do with enhanced pairing correlations in the nuclear surface. It is\nshown that in nuclei the coherence length is not a good indicator of the\nintensity of pairing correlations. This feature is contrasted with the\nsituation in infinite matter.", "category": "nucl-th" }, { "text": "Antiproton-deuteron annihilation at low energies: Recent experimental studies of the antiproton-deuteron system at low energies\nhave shown that the imaginary part of the antiproton-deuteron scattering length\nis smaller than the antiproton-proton one. Two- and three-body systems with\nstrong annihilation are investigated and a mechanism explaining this unexpected\nrelation between the imaginary parts of the scattering lengths is proposed.", "category": "nucl-th" }, { "text": "Resolving the plasma profile via differential single inclusive\n suppression: The ability of experimental signatures to resolve the spatio-temporal profile\nof an expanding quark gluon plasma is studied. In particular, the single\ninclusive suppression of high momentum hadrons versus the centrality of a\nheavy-ion collision and with respect to the reaction plane in non-central\ncollisions is critically examined. Calculations are performed in the higher\ntwist formalism for the modification of the fragmentation functions. Radically\ndifferent nuclear geometries are used. The influence of different initial gluon\ndistributions as well as different temporal evolution scenarios on the single\ninclusive suppression of high momentum pions are outlined. It is demonstrated\nthat the modification versus the reaction plane is quite sensitive to the\ninitial spatial density. Such sensitivity remains even in the presence of a\nstrong elliptic flow.", "category": "nucl-th" }, { "text": "Energy dependence of fission-fragment neutron multiplicity in\n $^{235}\\textrm{U}(n,f)$: A consistent framework for treating the energy dependence of fission-fragment\nneutron multiplicities is presented. The shape evolution of the compound\nnucleus towards scission is treated in the strong damping limit using the\nMetropolis walk method. The available excitation energy at scission is then\ndivided statistically between the two fragments using microscopic level\ndensities. Deformation energies, which contribute to the excitation energy when\nthe fragments relax to their ground-state shapes, are also computed. From the\ntotal fragment excitation energies, the number of emitted neutrons is obtained\nand illustrated for neutron-induced fission of $^{235}\\textrm{U}$.", "category": "nucl-th" }, { "text": "Cluster radioactivity of Th isotopes in the mean-field HFB theory: Cluster radioactivity is described as a very mass asymmetric fission process.\nThe reflection symmetry breaking octupole moment has been used in a mean field\nHFB theory as leading coordinate instead of the quadrupole moment usually used\nin standard fission calculations. The procedure has been applied to the study\nof the ``very mass asymmetric fission barrier'' of several even-even Thorium\nisotopes. The masses of the emitted clusters as well as the corresponding\nhalf-lives have been evaluated on those cases where experimental data exist.", "category": "nucl-th" }, { "text": "Nuclear structure and decay properties of even-even nuclei in $Z=70-80$\n drip-line region: We study nuclear structure properties for various isotopes of Ytterbium (Yb),\nHafnium(Hf), Tungsten(W), Osmium(Os), Platinum(Pt) and Mercury(Hg) in $Z = 70 -\n80$ drip-line region starting from $N =80$ to $N=170$ within the formalism of\nrelativistic mean field (RMF) theory. The pairing correlation is taken care by\nusing BCS approach. We compared our results with Finite Range Droplet\nModel(FRDM) and experimental data and found that the calculated results are in\ngood agreement. Neutron shell closure are obtained at $N=82$ and $126$ in this\nregion. We have also studied probable decay mechanisms of these elements.", "category": "nucl-th" }, { "text": "Anharmonic double-$\u03b3$ vibrations in nuclei and their description in\n the interacting boson model: Double-$\\gamma$ vibrations in deformed nuclei are studied in the context of\nthe interacting boson model with special reference to their anharmonic\ncharacter. It is shown that large anharmonicities can be obtained with\ninteractions that are (at least) of three-body nature between the bosons. As an\nexample the $\\gamma$ vibrations of the nucleus\n$^{166}_{\\phantom{0}68}$Er$^{\\phantom{00}}_{98}$ are studied in detail.", "category": "nucl-th" }, { "text": "Hadronic resonance production and interaction in partonic and hadronic\n matter in EPOS3 with and without the hadronic afterburner UrQMD: We study the production of hadronic resonances and their interaction in the\npartonic and hadronic medium using the EPOS3 model, which employs the UrQMD\nmodel for the description of the hadronic phase. We investigate the centrality\ndependence of the yields and momentum distributions for various resonances\n(rho(770),K(892),phi(1020),Delta(1232),Sigma(1385),Lambda(1520),Xi(1530) and\ntheir antiparticles) in Pb-Pb collisions at sNN= 2.76 TeV. The predictions for\nK(892) and phi(1020) will be compared with the experimental data from the ALICE\ncollaboration. The observed signal suppression of the K(892) with increasing\ncentrality will be discussed with respect to the resonance interaction in the\nhadronic medium. The mean transverse momentum and other particle ratios such as\nphi(1020)/p and Omega/phi(1020) will be discussed with respect to additional\ncontributions from the hadronic medium interactions.", "category": "nucl-th" }, { "text": "Nuclear energy density functional from chiral pion-nucleon dynamics: We calculate the nuclear energy density functional relevant for N=Z even-even\nnuclei in the systematic framework of chiral perturbation theory. The\ncalculation includes the one-pion exchange Fock diagram and the iterated\none-pion exchange Hartree and Fock diagrams. From these few leading order\ncontributions in the small momentum expansion one obtains already a very good\nequation of state of isospin symmetric nuclear matter. We find that in the\nregion below nuclear matter saturation density the effective nucleon mass\n$\\widetilde M^*(\\rho)$ deviates by at most 15% from its free space value $M$,\nwith $0.89M<\\widetilde M^*(\\rho)M$ for higher densities. The parameterfree strength of\nthe $(\\vec\\nabla \\rho)^2$-term, $F_\\nabla(k_f)$, is at saturation density\ncomparable to that of phenomenological Skyrme forces. The magnitude of\n$F_J(k_f)$ accompanying the squared spin-orbit density $\\vec J ^2$ comes out\nsomewhat larger. The strength of the nuclear spin-orbit interaction,\n$F_{so}(k_f)$, as given by iterated one-pion exchange is about half as large as\nthe corresponding empirical value, however, with the wrong negative sign. The\nnovel density dependencies of $\\widetilde M^*(\\rho)$ and $F_{\\nabla,so,J}(k_f)$\nas predicted by our parameterfree calculation should be examined in nuclear\nstructure calculations (after introducing an additional short range spin-orbit\ncontribution constant in density).", "category": "nucl-th" }, { "text": "Rapidity correlations test stochastic hydrodynamics: We show that measurements of the rapidity dependence of transverse momentum\ncorrelations can be used to determine the characteristic time $\\tau_{\\pi}$ that\ndictates the rate of isotropization of the stress energy tensor, as well as the\nshear viscosity $\\nu = \\eta/sT$. We formulate methods for computing these\ncorrelations using second order dissipative hydrodynamics with noise. Current\ndata are consistent with $\\tau_{\\pi}/\\nu \\sim 10$ but targeted measurements can\nimprove this precision.", "category": "nucl-th" }, { "text": "Nucleons and nuclei in the context of low-energy QCD: This presentation reports on recent developments concerning basic aspects of\nlow-energy QCD as they relate to the understanding of the nucleon mass and the\nnuclear many-body problem.", "category": "nucl-th" }, { "text": "Quark-meson coupling model for a nucleon: We considered the quark-meson coupling model for a nucleon. The model\ndescribes a nucleon as an MIT bag, in which quarks are coupled to the scalar\nand the vector mesons. A set of coupled equations for the quark and the meson\nfields are obtained and are solved in a self-consistent manner. We show that\nthe mass of a dressed MIT bag interacting with $\\sigma$- and $\\omega$-meson\nfields differs considerably from the mass of the free MIT bag. The effects of\nthe density-dependent bag constant are investigated. The results of our\ncalculations imply that the self-energy of the bag in the quark-meson coupling\nmodel is significant and needs to be considered in doing the calculations for\nnuclear matter or finite nuclei.", "category": "nucl-th" }, { "text": "Event-by-event distributions of azimuthal asymmetries in\n ultrarelativistic heavy-ion collisions: Relativistic dissipative fluid dynamics is a common tool to describe the\nspace-time evolution of the strongly interacting matter created in\nultrarelativistic heavy-ion collisions. For a proper comparison to experimental\ndata, fluid-dynamical calculations have to be performed on an event-by-event\nbasis. Therefore, fluid dynamics should be able to reproduce, not only the\nevent-averaged momentum anisotropies, $$, but also their distributions.\nIn this paper, we investigate the event-by-event distributions of the\ninitial-state and momentum anisotropies $\\epsilon_n$ and $v_n$, and their\ncorrelations. We demonstrate that the event-by-event distributions of relative\n$v_n$ fluctuations are almost equal to the event-by-event distributions of\ncorresponding $\\epsilon_n$ fluctuations, allowing experimental determination of\nthe relative anisotropy fluctuations of the initial state. Furthermore, the\ncorrelation $c(v_2,v_4)$ turns out to be sensitive to the viscosity of the\nfluid providing an additional constraint to the properties of the strongly\ninteracting matter.", "category": "nucl-th" }, { "text": "Phases of Dense Quark Matter and the Structure of Compact Objects: The presence of quark matter in neutron stars may affect several neutron star\nobservables and the neutrino signal in core-collapse supernovae. These\nobservables are sensitive to the phase of quark matter that is present in\ncompact objects. We present the first calculation of the phase structure of\ndense quark matter which includes a six-fermion color-superconducting\ninteraction and show that the effect of this term can destabilize the pairing\ninteraction, favoring phases where fewer quarks are paired. In turn, this\nmodification of the phase structure can modify the neutrino signal, the\nstructure of the neutron star, and the long-term cooling. We also show that,\ncontrary to the 20-year old paradigm of the surface structure of the\n\"strange-quark stars\", the surface of these objects may consist of nuggets of\nstrange quark matter screened by the electron gas.", "category": "nucl-th" }, { "text": "Supplemental note for \"Two-fermion emission from spin-singlet and\n triplet resonances in one dimension\": Time-dependent calculation has been a suitable method to investigate the\nquantum dynamical processes. In Ref. [1] = [T. Oishi et al., J. of Phys. G 45,\n105101 (2018)], we applied this method to the one-dimensional two-fermion\ntunneling in the nuclear-physics scale. Beside the specific results presented\ntherein, some basic formalism and methods, which can be helpful for further\ndiscussions and developments to investigate time-dependent quantum systems,\nhave been awaiting our description. This note is devoted to describe those\nsupplemental contents. We do not limit the story to the nuclear physics, but\nkeep it applicable to other scales and/or targets.", "category": "nucl-th" }, { "text": "Does quark-gluon plasma feature an extended hydrodynamic regime?: We investigate the response of the near-equilibrium quark-gluon plasma (QGP)\nto perturbation at non-hydrodynamic gradients. We propose a conceivable\nscenario under which sound mode continues to dominate the medium response in\nthis regime. Such a scenario has been observed experimentally for various\nliquids and liquid metals. We further show this extended hydrodynamic regime\n(EHR) indeed exists for both the weakly-coupled kinetic equation in the\nrelaxation time approximation (RTA) and the strongly-coupled ${\\cal N}=4$\nsupersymmetric Yang-Mills (SYM) theory. We construct a simple but nontrivial\nextension of M{\\\"u}eller-Isareal-Stewart (MIS) theory, namely MIS*, and\ndemonstrate that it describes EHR response for both RTA and SYM theory. This\nindicates that MIS* equations can potentially be employed to search for QGP EHR\nvia heavy-ion collisions.", "category": "nucl-th" }, { "text": "A percolation transition in Yang-Mills matter at finite number of\n colours: We examine baryonic matter at quark chemical potential of the order of the\nconfinement scale, $\\mu_q\\sim \\lqcd$. In this regime, quarks are supposed to be\nconfined but baryons are close to the ``tightly packed limit'' where they\nnearly overlap in configuration space. We show that this system will exhibit a\npercolation phase transition {\\em when varied in the number of colours} $N_c$:\nat high $N_c$, large distance correlations at quark level are possible even if\nthe quarks are essentially confined. At low $N_c$, this does not happen. We\ndiscuss the relevance of this for dense nuclear matter, and argue that our\nresults suggest a new ``phase transition'', varying $N_c$ at constant $\\mu_q$.", "category": "nucl-th" }, { "text": "Pairing and specific heat in hot nuclei: The thermodynamics of pairing phase-transition in nuclei is studied in the\ncanonical ensemble and treating the pairing correlations in a\nfinite-temperature variation after projection BCS approach (FT-VAP). Due to the\nrestoration of particle number conservation, the pairing gap and the specific\nheat calculated in the FT-VAP approach vary smoothly with the temperature,\nindicating a gradual transition from the superfluid to the normal phase, as\nexpected in finite systems. We have checked that the predictions of the FT-VAP\napproach are very accurate when compared to the results obtained by an exact\ndiagonalization of the pairing Hamiltonian. The influence of pairing\ncorrelations on specific heat is analysed for the isotopes $^{161,162}$Dy and\n$^{171,172}$Yb. It is shown that the FT-VAP approach, applied with a level\ndensity provided by mean field calculations and supplemented, at high energies,\nby the level density of the back-shifted Fermi gas model, can approximate\nreasonably well the main properties of specific heat extracted from\nexperimental data. However, the detailed shape of the calculated specific heat\nis rather sensitive to the assumption made for the mean field.", "category": "nucl-th" }, { "text": "Model independent study of massive lepton elastic scattering on the\n proton, beyond the Born approximation: Model independent expressions for all polarization observables in $\\mu+p\\to\n\\mu+p$ elastic scattering are obtained, taking into account the lepton mass and\nincluding the two-photon exchange contribution. The spin structure of the\nmatrix element is parametrized in terms of six independent complex amplitudes,\nfunctions of two independent kinematical variables. General statements about\nthe influence of the two--photon--exchange terms on the differential cross\nsection and on polarization observables are given. Polarization effects have\nbeen investigated for the case of a longitudinally polarized lepton beam and\npolarized nucleon in the final state.", "category": "nucl-th" }, { "text": "The Structure of the Hadron-Quark Reaction Zone: Hadron-quark combustion in dense matter is a central topic in the study of\nphases in compact stars and their high-energy astrophysics. We critically\nreview the literature on hadron-quark combustion, dividing them into a \"first\nwave\" that treats the problem as a steady-state burning with or without\nconstraints of mechanical equilibrium, and a \"second wave\" which uses numerical\ntechniques to resolve the burning front and solves the underlying Partial\nDifferential Equations for the chemistry of the burning front under less\nrestrictive conditions. We detail the inaccuracies that the second wave amends\nover the first wave, and highlight crucial differences between various\napproaches in the second wave. We also include results from time-dependent\nsimulations of the reaction zone that include a hadronic EOS, neutrinos, and\nself-consistent thermodynamics without using parameterized shortcuts.", "category": "nucl-th" }, { "text": "Universal behavior of $p$-wave proton-proton fusion near threshold: We calculate the $p$-wave contribution to the proton-proton fusion $S$ factor\nand its energy derivative in pionless effective field theory (EFT) up to\nnext-to-leading order. The leading contributions are given by a recoil piece\nfrom the Gamow-Teller and Fermi operators, and from relativistic $1/m$\nsuppressed weak interaction operators. We obtain the value of $(2.5\\pm0.3\n)\\times 10^{-28}~\\mathrm{MeV\\ fm^2}$ for the $S$ factor and $(2.2\\pm0.2) \\times\n10^{-26}~\\mathrm{fm^2}$ for its energy derivative at threshold. These are\nsmaller than the results of a prior study that employed chiral EFT by several\norders of magnitude. We conclude that, contrary to what has been previously\nreported, the $p$-wave contribution does not need to be considered in a\nhigh-precision determination of the $S$ factor at astrophysical energies.\nCombined with the chiral EFT calculation of Acharya {\\it et al.} [Phys. Lett. B\n\\bf{760}, 584 (2016)] for the $s$-wave channel, this gives a total threshold\n$S$ factor of $S(0) = (4.047^{+0.024}_{-0.032}) \\times 10^{-23}~{\\rm\nMeV~fm}^2$.", "category": "nucl-th" }, { "text": "In-Medium Vector Mesons, Dileptons and Chiral Restoration: Medium modifications of the electromagnetic spectral function in hadronic and\nquark-gluon matter are reviewed. A strong broadening of the $\\rho$ meson, which\ndominates the spectral function in the low-mass regime, is quantitatively\nconsistent with dilepton excess spectra measured in photoproduction off cold\nnuclei (CLAS/JLab) and in fixed-target ultrarelativistic heavy-ion collisions\n(NA45,NA60/CERN-SPS). The large excess observed by PHENIX at RHIC remains\nunexplained to date, but is most likely not due to emission from the\nQuark-Gluon Plasma. Connections to thermal lattice QCD promise progress in the\nsearch for chiral symmetry restoration.", "category": "nucl-th" }, { "text": "Fission-fragment mass distributions from strongly damped shape evolution: Random walks on five-dimensional potential-energy surfaces were recently\nfound to yield fission-fragment mass distributions that are in remarkable\nagreement with experimental data. Within the framework of the Smoluchowski\nequation of motion, which is appropriate for highly dissipative evolutions, we\ndiscuss the physical justification for that treatment and investigate the\nsensitivity of the resulting mass yields to a variety of model ingredients,\nincluding in particular the dimensionality and discretization of the shape\nspace and the structure of the dissipation tensor. The mass yields are found to\nbe relatively robust, suggesting that the simple random walk presents a useful\ncalculational tool. Quantitatively refined results can be obtained by including\nphysically plausible forms of the dissipation, which amounts to simulating the\nBrownian shape motion in an anisotropic medium.", "category": "nucl-th" }, { "text": "Applications of the Similarity Renormalization Group to the Nuclear\n Interaction: The Similarity Renormalization Group (SRG) is investigated as a powerful yet\npractical method to modify nuclear potentials so as to reduce computational\nrequirements for calculations of observables. The key feature of SRG\ntransformations that leads to computational benefits is the decoupling of\nlow-energy nuclear physics from high-energy details of the inter-nucleon\ninteraction. We examine decoupling quantitatively for two-body observables and\nfew-body binding energies. The universal nature of this decoupling is\nillustrated and errors from suppressing high-momentum modes above the\ndecoupling scale are shown to be perturbatively small. To explore the SRG\nevolution of many-body forces, we use as a laboratory a one-dimensional system\nof bosons with short-range repulsion and mid-range attraction, which emulates\nrealistic nuclear forces. The free-space SRG is implemented for few-body\nsystems in a symmetrized harmonic oscillator basis using a recursive\nconstruction analogous to no-core shell model implementations. Building on\none-dimensional results we performed the first practical evolution of\nthree-dimensional many-body forces within the No-Core Shell Model basis.\nResults for the 3H binding energy are consistent with previous calculations\ninvolving momentum-space evolution of only two-body forces, and validate\nexpectations from calculations in the one-dimensional oscillator basis. When\napplied to 4He calculations, the two- and three-body oscillator matrix elements\nyield rapid convergence of the ground-state energy with a small net\ncontribution of the induced four-body force. The radius of light nuclei is also\nexplored in the three-dimensional basis.", "category": "nucl-th" }, { "text": "The generalised relativistic Lindhard functions: We present here analytic expressions for the generalised Lindhard function,\nalso referred to as Fermi Gas polarisation propagator, in a relativistic\nkinematic framework and in the presence of various resonances and vertices.\nParticular attention is payed to its real part, since it gives rise to\nsubstantial difficulties in the definition of the currents entering the\ndynamics.", "category": "nucl-th" }, { "text": "Soft two-meson-exchange nucleon-nucleon potentials. II. One-pair and\n two-pair diagrams: Two-meson-exchange nucleon-nucleon potentials are derived where either one or\nboth nucleons contains a pair vertex. Physically, the meson-pair vertices are\nmeant to describe in an effective way (part of) the effects of heavy-meson\nexchange and meson-nucleon resonances. {}From the point of view of ``duality,''\nthese two kinds of contribution are roughly equivalent. The various\npossibilities for meson pairs coupling to the nucleon are inspired by the\nchiral-invariant phenomenological Lagrangians that have appeared in the\nliterature. The coupling constants are fixed using the linear $\\sigma$ model.\nWe show that the inclusion of these two-meson exchanges gives a significant\nimprovement over a potential model including only the standard one-boson\nexchanges.", "category": "nucl-th" }, { "text": "Mechanisms producing fissionlike binary fragments in heavy collisions: The mixing of the quasifission component to the fissionlike cross section\ncauses ambiguity in the quantitative estimation of the complete fusion cross\nsection from the observed angular and mass distributions of the binary\nproducts. We show that the partial cross section of quasifission component of\nbinary fragments covers the whole range of the angular momentum values leading\nto capture. The calculated angular momentum distributions for the compound\nnucleus and dinuclear system going to quasifission may overlap: competition\nbetween complete fusion and quasifission takes place at all values of initial\norbital angular momentum. Quasifission components formed at large angular\nmomentum of the dinuclear system can show isotropic angular distribution and\ntheir mass distribution can be in mass symmetric region similar to the\ncharacteristics of fusion-fission components. As result the unintentional\ninclusion of the quasifission contribution into the fusion-fission fragment\nyields can lead to overestimation of the probability of the compound nucleus\nformation.", "category": "nucl-th" }, { "text": "Mass dependence and isospin dependence of short-range correlated pairs: The target-mass number dependence of nucleon-nucleon pairs with short-range\ncorrelations is explored in a physically transparent geometrical model within a\nzero-range approximation. The observed $A$ dependence of 2-nucleon ejection\ncross sections in $(e,e')$ reactions is found to reflect the mass dependence of\nnuclear density distributions. A parametrization of this $A$ dependence is\ngiven. The $A$ dependence of proton-proton vs.\\ proton-neutron pairs relative\nto $^{12}$C is also analyzed in this model. It can be understood using simple\ncombinatorics without any additional isospin dependence.", "category": "nucl-th" }, { "text": "A comparative analysis of in-medium spectral functions for $N(940)$ and\n $N^*(1535)$ in real-time thermal field theory: In the real-time thermal field theory, the nucleon self-energy at finite\ntemperature and density is evaluated where an extensive set of pion-baryon\n($\\pi B$) loops are considered. On the other side the in-medium self-energy of\n$N^*(1535)$ for $\\pi N$ and $\\eta N$ loops is also determined in the same\nframework. The detail branch cut structures for these different $\\pi B$ loops\nfor nucleon $N(940)$ and $\\pi N$, $\\eta N$ loops for $N^*(1535)$ are addressed.\nUsing the total self-energy of $N(940)$ and $N^*(1535)$, which contain the\ncontributions of their corresponding loop diagrams, the complete structures of\ntheir in-medium spectral functions have been obtained. The Landau and unitary\ncut contributions provide two separate peak structures in the nucleon spectral\nfunction while $N^*(1535)$ has single peak structure in its unitary cuts. At\nhigh temperature, the peak structures of both at their individual poles are\nattenuated while at high density Landau peak structure of nucleon is completely\nsuppressed and its unitary peak structure is tending to be shifted towards the\nmelted peak of $N^*(1535)$. The non-trivial modifications of these chiral\npartners may indicate some association of chiral symmetry restoration.", "category": "nucl-th" }, { "text": "Resonances from Baryon decuplet-Meson octet interaction: The s-wave interactions of the baryon decuplet with the octet of pseudoscalar\nmesons is studied in a unitarized coupled channel approach. We obtain a fair\nagreement for mass and width of several 3/2- resonances. In particular, the\nXi(1820), the Lambda(1520) and the Sigma(1670) states are well reproduced.\nOther resonances are predicted and also the couplings of the observed\nresonances to the various channels are evaluated.", "category": "nucl-th" }, { "text": "Quantum Monte Carlo calculations of electromagnetic transitions in 8Be\n with meson-exchange currents derived from chiral effective field theory: We report quantum Monte Carlo calculations of electromagnetic transitions in\n8Be. The realistic Argonne v18 two-nucleon and Illinois-7 three-nucleon\npotentials are used to generate the ground state and nine excited states, with\nenergies that are in excellent agreement with experiment. A dozen M1 and eight\nE2 transition matrix elements between these states are then evaluated. The E2\nmatrix elements are computed only in impulse approximation, with those\ntransitions from broad resonant states requiring special treatment. The M1\nmatrix elements include two-body meson-exchange currents derived from chiral\neffective field theory, which typically contribute 20--30% of the total\nexpectation value. Many of the transitions are between isospin-mixed states;\nthe calculations are performed for isospin-pure states and then combined with\nempirical mixing coefficients to compare to experiment. Alternate mixings are\nalso explored. In general, we find that transitions between states that have\nthe same dominant spatial symmetry are in reasonable agreement with experiment,\nbut those transitions between different spatial symmetries are often\nunderpredicted.", "category": "nucl-th" }, { "text": "The Disappearance of Flow: We investigate the disappearance of collective flow in the reaction plane in\nheavy-ion collisions within a microscopic model (QMD). A systematic study of\nthe impact parameter dependence is performed for the system Ca+Ca. The balance\nenergy strongly increases with impact parameter. Momentum dependent\ninteractions reduce the balance energies for intermediate impact parameters\n$b\\approx4.5$ fm. Dynamical negative flow is not visible in the laboratory\nframe but does exist in the contact frame for the heavy system Au+Au. For\nsemi-peripheral collisions of Ca+Ca with $b\\approx6.5$ fm a new two-component\nflow is discussed. Azimuthal distributions exhibit strong collectiv flow\nsignals, even at the balance energy.", "category": "nucl-th" }, { "text": "Analysis of the data on spin density matrix elements for $\u03b3p \\to\n K^{*+}\u039b$: In our previous work [Phys. Rev. C {\\bf 96}, 035206 (2017)], the\nhigh-precision differential cross-section data for $\\gamma p \\to K^{*+}\\Lambda$\nreported by the CLAS Collaboration has been analyzed within an effective\nLagrangian approach. It was found that apart from the $t$-channel $K$, $K^*$,\nand $\\kappa$ exchanges, the $u$-channel $\\Lambda$, $\\Sigma$, and $\\Sigma^*$\nexchanges, the $s$-channel $N$ exchange, and the interaction current, one needs\nto introduce at least two nucleon resonances in the $s$ channel in constructing\nthe reaction amplitudes to describe the cross-section data. One of the needed\nresonances is $N(2060)5/2^-$, and the other one could be one of the\n$N(2000)5/2^+$, $N(2040)3/2^+$, $N(2100)1/2^+$, $N(2120)3/2^-$, and\n$N(2190)7/2^-$ resonances. In this paper, we further include in our analysis\nthe data on spin density matrix elements for $K^*$ meson reported recently by\nthe CLAS Collaboration, with the purpose being to impose further constraints on\nextracting the resonance contents and to gain a better understanding of the\nreaction mechanism. It turns out that with the new data on spin density matrix\nelements taken into account, only the set with the $N(2060)5/2^-$ and\n$N(2000)5/2^+$ resonances among those five possible solutions extracted from\nthe analysis of the differential cross-section data can satisfactorily describe\nthe data on both the differential cross sections and the spin density matrix\nelements. Further analysis shows that this reaction is dominated by the\n$t$-channel $K$ exchange and $s$-channel $N(2060)5/2^-$ and $N(2000)5/2^+$\nexchanges.", "category": "nucl-th" }, { "text": "Spectral Function of rho in Dense and Hot Hadronic Matter: The spectral function of rho meson in hot/dense hadronic matter is studied by\ntaking into account the nucleon-loop on quantum hadrondynamics model level.\nDifferent from the hot pion gas effect which changes the spectral function\nslightly, the nucleon-antinucleon polarization (Dirac sea) makes the spectral\nfunction very sharp and shifted towards the low invariant mass region\nsignificantly due to the decreasing effective nucleon mass.", "category": "nucl-th" }, { "text": "Collectivity in Ultra-Peripheral Pb+Pb Collisions at the Large Hadron\n Collider: We present the first full (3+1)D dynamical simulations of ultra-peripheral\nPb+Pb collisions at the Large Hadron Collider. Extrapolating from p+Pb\ncollisions, we explore whether a quasi-real photon $\\gamma^*$ interacting with\nthe lead nucleus in an ultra-peripheral collision can create a many-body system\nexhibiting fluid behavior. Assuming strong final-state interactions, we provide\nmodel results for charged hadron multiplicity, identified particle mean\ntransverse momenta, and charged hadron anisotropic flow coefficients, and\ncompare them with experimental data from the ALICE and ATLAS collaborations.\nThe elliptic flow hierarchy between p+Pb and $\\gamma^*$+Pb collisions is\ndominated by the difference in longitudinal flow decorrelations and reproduces\nthe experimental data well. We have demonstrated that our theoretical framework\nprovides a quantitative tool to study particle production and collectivity for\nall system sizes, ranging from central heavy-ion collisions to small asymmetric\ncollision systems at the Relativistic Heavy-Ion Collider and the Large Hadron\nCollider and even at the future Electron-Ion Collider.", "category": "nucl-th" }, { "text": "The Magnetic Moments of the Octet Baryons in Quenched Chiral\n Perturbation Theory: We compute the magnetic moments of the octet baryons up to two orders in\nquenched chiral perturbation theory. In addition to the $\\sim\\sqrt{m_q}$\ncontributions that arise in QCD, there are lower-order contributions of the\nform $M_0^2\\log m_q$ from loop diagrams involving hairpin interactions.", "category": "nucl-th" }, { "text": "Non-equilibrium approaches to the pre-thermal and post-hadronisation\n stages of A+A collisions: The results related to non-equilibrium phenomena at the very early and late\nstages of the processes of A+A collisions are presented. A good description of\nthe hadron momentum spectra as well as pion and kaon interferometry data at\nRHIC is reached within the realistic dynamical picture of A+A collisions:\nHydroKinetic Model (HKM). The model accumulates the following features: not too\nearly thermalization time; $\\tau\\geq 1$ fm/c; a developing of the pre-thermal\ntransverse flows; the effectively more hard, than in the case of chemical\nequilibrium, equation of state of expanding chemically non-equilibrated\nmulti-hadronic gas; a continuous non-equilibrated emission of hadrons. All\nthese factors lead to a good description of the mentioned RHIC data, in\nparticular, the observed $R_{out}/R_{side}$ ratios, solving, therefore, the HBT\npuzzle in detailed realistic model.", "category": "nucl-th" }, { "text": "Target mass number dependence of subthreshold antiproton production in\n proton-, deuteron- and alpha-particle-induced reactions: Data from KEK on subthreshold $\\bar{\\mrm{p}}$ as well as on $\\pi^\\pm$ and\n$\\mrm{K}^\\pm$ production in proton-, deuteron- and $\\alpha$-induced reactions\nat energies between 2.0 and 12.0 A GeV for C, Cu and Pb targets are described\nwithin a unified approach. We use a model which considers a nuclear reaction as\nan incoherent sum over collisions of varying numbers of projectile and target\nnucleons. It samples complete events and thus allows for the simultaneous\nconsideration of all final particles including the decay products of the\nnuclear residues. The enormous enhancement of the $\\bar{\\mrm{p}}$ cross\nsection, as well as the moderate increase of meson production in deuteron and\n$\\alpha$ induced compared to proton-induced reactions, is well reproduced for\nall target nuclei. In our approach, the observed enhancement near the\nproduction threshold is mainly due to the contributions from the interactions\nof few-nucleon clusters by simultaneously considering fragmentation processes\nof the nuclear residues. The ability of the model to reproduce the target mass\ndependence may be considered as a further proof of the validity of the cluster\nconcept.", "category": "nucl-th" }, { "text": "Proton-Proton and Proton-Neutron Correlations in Medium-Weight Nuclei:\n Role of the Tensor Force within a Many-Body Cluster Expansion: A detailed analysis of the effect of tensor correlations on one- and two-body\ndensities and momentum distributions of complex nuclei is presented within a\nlinked cluster expansion providing reliable results for the ground state\nproperties of nuclei calculated with realistic interactions.", "category": "nucl-th" }, { "text": "Femtoscopy in Relativistic Heavy Ion Collisions and its Relation to Bulk\n Properties of QCD Matter: Using a viscous hydrodynamic model coupled to a hadronic cascade code,\nnumerous features of the dynamics and equilibrium properties are explored for\ntheir impact on femtoscopic measurements. The equation of state, viscous\nparameters and initial conditions are investigated. We find that femtoscopy is\naffected by numerous model features at the 10% level, and that by including\nfeatures and adjusting unknown parameters, one can explain experimental source\nsize measurements to better than 10%.", "category": "nucl-th" }, { "text": "Probing the pairing interaction through two-neutron transfer reactions: Cross sections for ($p,t$) two-neutron transfer reactions are calculated in\nthe one-step zero-range distorted-wave Born approximation for the tin isotopes\n$^{124}$Sn and $^{136}$Sn and for incident proton energies from 15 to 35 MeV.\nMicroscopic quasiparticle random-phase approximation form factors are provided\nfor the reaction calculation and phenomenological optical potentials are used\nin both the entrance and the exit channels. Three different surface/volume\nmixings of a zero-range density-dependent pairing interaction are employed in\nthe microscopic calculations and the sensitivity of the cross sections to the\ndifferent mixings is analyzed. Since absolute cross sections cannot be obtained\nwithin our model, we compare the positions of the diffraction minima and the\nshapes of the angular distributions. No differences are found in the position\nof the diffraction minima for the reaction $^{124}$Sn($p,t$)$^{122}$Sn. On the\nother side, the angular distributions obtained for the reaction\n$^{136}$Sn($p,t$)$^{134}$Sn with surface and mixed interactions differ at large\nangles for some values of the incident proton energy. For this reaction, we\ncompare the ratios of the cross sections associated to the ground state and the\nfirst excited state transitions. Differences among the three different\ntheoretical predictions are found and they are more important at the incident\nproton energy of 15 MeV. As a conclusion, we indicate ($p,t$) two-neutron\ntransfer reactions with very neutron-rich Sn isotopes and at proton energies\naround 15 MeV as good experimental cases where the surface/volume mixing of the\npairing interaction may be probed.", "category": "nucl-th" }, { "text": "Statistical aspects of nuclear coupling to continuum: Various global characteristics of the coupling between the bound and\nscattering states are explicitly studied based on realistic Shell Model\nEmbedded in the Continuum. In particular, such characteristics are related to\nthose of the scattering ensemble. It is found that in the region of higher\ndensity of states the coupling to continuum is largely consistent with the\nstatistical model. However, assumption of channel equivalence in the\nstatistical model is, in general, violated.", "category": "nucl-th" }, { "text": "Measuring the Rate of Isotropization of Quark-Gluon Plasma Using\n Rapidity Correlations: We propose that rapidity dependent momentum correlations can be used to\nextract the shear relaxation time $\\tau_\\pi$ of the medium formed in high\nenergy nuclear collisions. The stress-energy tensor in an equilibrium\nquark-gluon plasma is isotropic, but in nuclear collisions it is likely very\nfar from this state. The relaxation time $\\tau_\\pi$ characterizes the rate of\nisotropization and is a transport coefficient as fundamental as the shear\nviscosity. We show that fluctuations emerging from the initial anisotropy\nsurvive to freeze-out, in excess of thermal fluctuations, influencing rapidity\ncorrelation patterns. We show that these correlations can be used to extract\n$\\tau_\\pi$. We describe a method for calculating the rapidity dependence of\ntwo-particle momentum correlations with a second order, causal, diffusion\nequation that includes Langevin noise as a source of thermal fluctuations. The\ncausality requirement introduces the relaxation time and we link the shape of\nthe rapidity correlation pattern to its presence. Here we examine how different\nequations of state and temperature dependent transport coefficients in the\npresence of realistic hydrodynamic flow influence the estimate of $\\tau_\\pi$.\nIn comparison to RHIC data, we find that the ratio $\\tau_\\pi/\\nu \\approx 5-6$\nwhere $\\nu=\\eta/sT$ is the kinematic viscosity.", "category": "nucl-th" }, { "text": "Convergence and efficiency of angular momentum projection for many-body\n systems: In many so-called \"beyond-mean-field\" many-body methods, one creates\nsymmetry-breaking states and then projects out states with good quantum\nnumber(s); the most important example is angular momentum. Motivated by the\ncomputational intensity of symmetry restoration, we investigate the numerical\nconvergence of two competing methods for angular momentum projection with\nrotations over Euler angles, the textbook-standard projection through\nquadrature, and a recently introduced projection through linear algebra. We\nfind well-defined patterns of convergence with increasing number of mesh points\n(for quadrature) and cut-offs (for linear algebra). Because the method of\nprojection through linear algebra requires inverting matrices generated on a\nmesh of Euler angles, we discuss two methods for robustly reducing the number\nof required evaluations. Reviewing the literature, we find our inversion\ninvolving rotations about the $z$-axis is equivalent to trapezoidal\n\"quadrature\" commonly used as well as Fomenko projection used for\nparticle-number projection. The efficiency depends upon the number of angular\nmomentum $J$ to be projected, but in general inversion methods, including\nFomenko projection/trapezoidal \"quadrature\" dramatically improve the\nefficiency.", "category": "nucl-th" }, { "text": "v4 for identified particles at RHIC from viscous hydrodynamics: Using ideal and viscous hydrodynamics, the ratio of azimuthal moments\nv4/(v2)^2 is calculated for pions, protons, and kaons in sqrt{s}=200 A*GeV\nAu+Au collisions. For any value of viscosity here is little dependence on\nparticle species. Ideal hydrodynamics and data show a flat curve as a function\nof pt. Adding viscosity in the standard way destroys this flatness. However, it\ncan be restored by replacing the standard quadratic ansatz for delta f (the\nviscous correction to the distribution function at freeze-out) with a weaker\nmomentum dependence.", "category": "nucl-th" }, { "text": "Deduction of the quantum numbers of low-lying states of 4-nucleon\n systems based on symmetry: The inherent nodal structures of the wavefunctions of 4-nucleon systems have\nbeen investigated. The quantum numbers of the excited states (resonances) have\nbeen deduced. It was found that all the T=0 even-parity resonances are\ndominated by {2,1,1} component with L=1, all the T=0 odd-parity resonances are\ndominated by {3,1} component with L=1, and all the T=1 odd-parity resonances\nare also dominated by {3,1} component with L=1. The understanding of the\ninherent nodal structure is found to be crucial to a systematic understanding\nof the spectrum.", "category": "nucl-th" }, { "text": "Addendum: Triton and hypertriton binding energies calculated from SU_6\n quark-model baryon-baryon interactions: Previously we calculated the binding energies of the triton and hypertriton,\nusing an SU_6 quark-model interaction derived from a resonating-group method of\ntwo baryon clusters. In contrast to the previous calculations employing the\nenergy-dependent interaction kernel, we present new results using a\nrenormalized interaction, which is now energy independent and reserves all the\ntwo-baryon data. The new binding energies are slightly smaller than the\nprevious values. In particular the triton binding energy turns out to be 8.14\nMeV with a charge-dependence correction of the two-nucleon force, 190 keV,\nbeing included. This indicates that about 350 keV is left for the energy which\nis to be accounted for by three-body forces.", "category": "nucl-th" }, { "text": "A new Perspective on the Scalar meson Puzzle, from Spontaneous Chiral\n Symmetry Breaking Beyond BCS: We introduce coupled channels of Bethe-Salpeter mesons both in the boundstate\nequation for mesons and in the mass gap equation for chiral symmetry.\nConsistency is insured by the Ward Identities for axial currents, which\npreserve the Goldstone boson nature of the pion and prevents a systematic shift\nof the hadron spectrum. We study the decay of a scalar meson coupled to a pair\nof pseudoscalars. We also show that coupled channels reduce the breaking of\nchiral symmetry, with the same Feynman diagrams that appear in the coupling of\na scalar meson to a pair of pseudoscalar mesons. Exact calculations are\nperformed in a particular confining quark model, where we find that the\ngroundstate $I=0, ^3P_0 q \\bar q$ meson is the f_0(980) with a partial decay\nwidth of 40MeV. We also find a 30% reduction of the chiral condensate due to\ncoupled channels.", "category": "nucl-th" }, { "text": "A new Microscopic Model for $J/\u03c8$ Production in Heavy Ion Collisions: We present a new model for the creation of \\J mesons in ultrarelativistic\nheavy ion collisions, which allows to follow the individual heavy quarks from\ntheir creation until the detector through the Quark Gluon Plasma (QGP), which\nis formed in these collisions and described by the EPOS2 event generator. The\n\\cc quarks interact via a potential, based on results of lattice gauge\ncalculations. The annihilation and creation of \\J is described by a density\nmatrix approach whose time evolution is studied in the expanding system. The\ncomparison with PbPb data at $\\sqrt{s}$=5.02 TeV shows that this model can\ndescribe simultaneously the nuclear modification factor $R_{AA}$ and the\nelliptic flow $v_2$ of the \\J at low transverse momen", "category": "nucl-th" }, { "text": "Quark Models of Baryon Masses and Decays: The application of quark models to the spectra and strong and electromagnetic\ncouplings of baryons is reviewed. This review focuses on calculations which\nattempt a global description of the masses and decay properties of baryons,\nalthough recent developments in applying large N_c QCD and lattice QCD to the\nbaryon spectrum are described. After outlining the conventional\none-gluon-exchange picture, models which consider extensions to this approach\nare contrasted with dynamical quark models based on Goldstone-boson exchange\nand an algebraic collective-excitation approach. The spectra and\nelectromagnetic and strong couplings that result from these models are compared\nwith the quantities extracted from the data and each other, and the impact of\nvarious model assumptions on these properties is emphasized. Prospects for the\nresolution of the important issues raised by these comparisons are discussed.", "category": "nucl-th" }, { "text": "$\u039b\u039b$ Interaction in a Nuclear Density Functional Theory and\n Hyperon Puzzle of the Neutron Star: A Skyrme-type effective potential is determined to describe the interaction\nbetween $\\Lambda$ hyperons in nuclear medium. Experimental data of the binding\nenergies of the double-$\\Lambda$ ($\\Lambda\\Lambda$) nuclei with mass numbers\n$A=10$--$13$ are used to fit the parameters of the $\\Lambda\\Lambda$\ninteraction. As a result of the fitting, we obtain eight different sets of the\n$\\Lambda\\Lambda$ interaction parameters, which reproduces the input data within\n5\\% deviation from the experimental data on average. The eight $\\Lambda\\Lambda$\ninteractions are plugged in the calculation of the heavier $\\Lambda\\Lambda$\nnuclei and the neutron star equation of state to explore the issue of hyperon\npuzzle. We found that the $\\Lambda\\Lambda$ interaction, specifically, p-wave\ninteraction makes the equation of state stiff enough that the maximum mass of\nthe neutron star can be as large as, or above $2\\;M_\\odot$.", "category": "nucl-th" }, { "text": "Properties of effective interactions and the excitation of 6- states in\n 28Si: Cross-section and analyzing power data from (p,p') scattering to the 6-\nstates at 11.58 and 14.35 MeV in 28Si, taken with energies of 80, 100, 134, and\n180 MeV protons, have been analyzed using a distorted wave approximation with\nmicroscopically defined wave functions. The results, taken in conjunction with\nan analysis of an M6 electron scattering form factor, suggest that the two\nstates exhaust respectively, ~50% and ~60% of the strengths of isoscalar and\nisovector particle-hole excitations from the ground state. The energy variation\nof data also suggests that the non-central components of the effective\ninteractions at 80 and 100 MeV may need to be enhanced.", "category": "nucl-th" }, { "text": "Dynamic Microscopic Theory of Fusion Using DC-TDHF: The density-constrained time-dependent Hartree-Fock (DC-TDHF) theory is a\nfully microscopic approach for calculating heavy-ion interaction potentials and\nfusion cross sections below and above the fusion barrier. We discuss recent\napplications of DC-TDHF method to fusion of light and heavy systems.", "category": "nucl-th" }, { "text": "Heavy quark diffusion from coherent color fields in relativistic\n heavy-ion collisions: The diffusion coefficients of heavy quarks from the coherent color\nelectromagnetic fields which are generated in the early stage of relativistic\nheavy-ion collisions are calculated at midrapidity, and compared with those\nobtained from collisions within a thermalized quark-gluon plasma. The coherent\ncolor fields are modeled such that they are initially longitudinal and then\nbecome isotropic. We found that the diffusion coefficients from the coherent\ncolor fields are larger than those from collisions except for very fast heavy\nquarks, and the color fields are less effective for heavy-quark energy loss.\nThe importance of coherent color fields for heavy-quark diffusion decreases as\nenergy density decreases.", "category": "nucl-th" }, { "text": "Dynamic nature at the QCD Critical End Point: This paper has been withdrawn by the authors due to inadequate arguments.", "category": "nucl-th" }, { "text": "A short course on Relativistic Heavy Ion Collisions: Some ideas/concepts in relativistic heavy ion collisions are discussed. To a\nlarge extent, the discussions are non-comprehensive and non-rigorous. It is\nintended for fresh graduate students of Homi Bhabha National Institute, Kolkata\nCentre, who are intending to pursue career in theoretical /experimental high\nenergy nuclear physics. Comments and criticisms will be appreciated.", "category": "nucl-th" }, { "text": "The Possible Origin and Implications of the Shoulder in Reactor Neutrino\n Spectra: We analyze within a nuclear database framework the shoulder observed in the\nantineutrino spectra in current reactor experiments. We find that the\nENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an\nanalogous shoulder in the aggregate fission beta spectra. In contrast, the\nJEFF-3.1.1 database does not predict a shoulder for two out of three of the\nmodern reactor neutrino experiments, and the shoulder that is predicted by\nJEFF-3.1.1 arises from $^{238}$U. We consider several possible origins of the\nshoulder, and find possible explanations. For example, there could be a problem\nwith the measured aggregate beta spectra, or the harder neutron spectrum at a\nlight-water power reactor could affect the distribution of beta-decaying\nisotopes. In addition to the fissile actinides, we find that $^{238}$U could\nalso play a significant role in distorting the total antineutrino spectrum.\nDistinguishing these and quantifying whether there is an anomaly associated\nwith measured reactor neutrino signals will require new short-baseline\nexperiments, both at thermal reactors and at reactors with a sizable epithermal\nneutron component.", "category": "nucl-th" }, { "text": "One-loop corrections to omega photoproduction near threshold: One-loop corrections to $\\omega$ photoproduction near threshold have been\ninvestigated by using the approximation that all relevant transition amplitudes\nare calculated from the tree diagrams of effective Lagrangians. With the\nparameters constrained by the data of $\\gamma N \\to \\pi N$, $\\gamma N \\to \\rho\nN$, and $\\pi N \\to \\omega N$ reactions, it is found that the one-loop effects\ndue to the intermediate $\\pi N$ and $\\rho N$ states can significantly change\nthe differential cross sections and spin observables. The results from this\nexploratory investigation suggest strongly that the coupled-channel effects\nshould be taken into account in extracting reliable resonance parameters from\nthe data of vector meson photoproduction in the resonance region.", "category": "nucl-th" }, { "text": "A possible explanation for AMS doubly charged anomalous event: By means of the quark mass density-dependent model, a possible explanation\nfor the doubly charged anomalous event with Z/A=0.114 reported by Alpha\nMagnetic Spectrometer Collaboration is given. It seems a strangelet. The\ncomposition, radius and mean lifetime of this strangelet are given.", "category": "nucl-th" }, { "text": "A microscopic equation of state for neutron-rich matter and its effect\n on neutron star properties: Chapter prepared for the book \"Astrophysics\", ISBN 979-953-307-389-6, INTECH\nPublishers (in press).", "category": "nucl-th" }, { "text": "A Combined Solution of the Schwinger-Dyson and Bethe-Salpeter Equations\n for Mesons as $q\\bar q$ Bound States: The mass spectrum of heavy pseudoscalar mesons, described as quark-antiquark\nbound systems, is considered within the Bethe-Salpeter formalism with momentum\ndependent masses of the constituents. This dependence is found by solving the\nSchwinger-Dyson equation for quark propagators in rainbow-ladder approximation.\nSuch an approximation is known to provide both a fast convergence of numerical\nmethods and accurate results for lightest mesons. However, as the meson mass\nincreases, the method becomes less stable and special attention must be devoted\nto details of numerical means of solving the corresponding equations. We focus\non the pseudoscalar sector and show that our numerical scheme describes fairly\naccurately the $\\pi$, $K$, $D$, $D_s$ and $\\eta_c$ ground states. Excited\nstates are considered as well. Our calculations are directly related to the\nfuture physics programme at FAIR.", "category": "nucl-th" }, { "text": "Signatures of three-nucleon interactions in few-nucleon systems: Recent experimental results in three-body systems have unambiguously shown\nthat calculations based only on nucleon-nucleon forces fail to accurately\ndescribe many experimental observables and one needs to include effects which\nare beyond the realm of the two-body potentials. This conclusion owes its\nsignificance to the fact that experiments and calculations can both be\nperformed with a high accuracy. In this review, both theoretical and\nexperimental achievements of the past decade will be underlined. Selected\nresults will be presented. The discussion on the effects of the three-nucleon\nforces is, however, limited to the hadronic sector. It will be shown that\ndespite the major successes in describing these seemingly simple systems, there\nare still clear discrepancies between data and the state-of-the-art\ncalculations.", "category": "nucl-th" }, { "text": "Variational Monte Carlo calculations of $\\mathbf{A\\leq 4}$ nuclei with\n an artificial neural-network correlator ansatz: The complexity of many-body quantum wave functions is a central aspect of\nseveral fields of physics and chemistry where non-perturbative interactions are\nprominent. Artificial neural networks (ANNs) have proven to be a flexible tool\nto approximate quantum many-body states in condensed matter and chemistry\nproblems. In this work we introduce a neural-network quantum state ansatz to\nmodel the ground-state wave function of light nuclei, and approximately solve\nthe nuclear many-body Schr\\\"odinger equation. Using efficient stochastic\nsampling and optimization schemes, our approach extends pioneering applications\nof ANNs in the field, which present exponentially-scaling algorithmic\ncomplexity. We compute the binding energies and point-nucleon densities of\n$A\\leq 4$ nuclei as emerging from a leading-order pionless effective field\ntheory Hamiltonian. We successfully benchmark the ANN wave function against\nmore conventional parametrizations based on two- and three-body Jastrow\nfunctions, and virtually-exact Green's function Monte Carlo results.", "category": "nucl-th" }, { "text": "Decay of Hypernuclei: We present a nonrelativistic transition potential for the weak\nstrangeness-changing reaction $\\Lambda N \\to NN$. The potential is based on a\none meson exchange model (OME), where, in addition to the long-ranged pion, the\nexchange of the pseudoscalar $K, \\eta$, as well as the vector $\\rho, \\omega,\nK^*$ mesons is considered. Results obtained for different hypernuclear decay\nobservables are compared to the available experimental data.", "category": "nucl-th" }, { "text": "Theoretical uncertainties of the elastic nucleon-deuteron scattering\n observables: Theoretical uncertainties of various types are discussed for the\nnucleon-deuteron elastic scattering observables at the incoming nucleon\nlaboratory energies up to 200 MeV. We are especially interested in the\nstatistical errors arising from uncertainties of parameters of a\nnucleon-nucleon interaction. The obtained uncertainties of the differential\ncross section and numerous scattering observables are in general small, grow\nwith the reaction energy and amount up to a few percent at 200 MeV. We compare\nthese uncertainties with the other types of theoretical errors like truncation\nerrors, numerical uncertainties and uncertainties arising from using the\nvarious models of nuclear interaction. We find the latter ones to be dominant\nsource of uncertainties of modern predictions for the three-nucleon scattering\nobservables. To perform above mentioned studies we use the One-Pion-Exchange\nGaussian potential derived by the Granada group, for which the covariance\nmatrix of its parameters is known, and solve the Faddeev equation for the\nnucleon-deuteron elastic scattering. Thus beside studying theoretical\nuncertainties we also show a description of the nucleon-deuteron elastic\nscattering data by the One-Pion-Exchange Gaussian model and compare it with\nresults obtained with other nucleon-nucleon potentials, including chiral\nN$^4$LO forces from the Bochum-Bonn and Moscow(Idaho)-Salamanca groups. In this\nway we confirm the usefulness and high quality of the One-Pion-Exchange\nGaussian force.", "category": "nucl-th" }, { "text": "The Weak Parity-Violating Pion-Nucleon Coupling (Revised): We use QCD sum rules to obtain the weak parity-violating pion-nucleon\ncoupling constant $f_{\\pi NN}$. We find that $f_{\\pi NN}\\approx 2\\times\n10^{-8}$, about an order of magnitude smaller than the ``best estimates'' based\non quark models. This result follows from the cancellation between perturbative\nand nonperturbative QCD processes not found in quark models, but explicit in\nthe QCD sum rule method. Our result is consistent with the experimental upper\nlimit found from $^{18}$F parity-violating measurements.", "category": "nucl-th" }, { "text": "Leading order relativistic hyperon-nucleon interactions in chiral\n effective field theory: We apply a recently proposed covariant power counting in nucleon-nucleon\ninteractions to study strangeness $S=-1$ $\\Lambda N-\\Sigma N$ interactions in\nchiral effective field theory. At leading order, Lorentz invariance introduces\n12 low energy constants, in contrast to the heavy baryon approach, where only\nfive appear. The Kadyshevsky equation is adopted to resum the potential in\norder to account for the non-perturbative nature of hyperon-nucleon\ninteractions. A fit to the $36$ hyperon-nucleon scattering data points yields\n$\\chi^2\\simeq 16$, which is comparable with the sophisticated phenomenological\nmodels and the next-to-leading order heavy baryon approach. However, one cannot\nachieve a simultaneous description of the nucleon-nucleon phase shifts and\nstrangeness $S=-1$ hyperon-nucleon scattering data at leading order.", "category": "nucl-th" }, { "text": "Resonance Structure and Polarizability of the nucleon: The main features of the resonance structure of the nucleon are discussed,\nparticular with regard to the helicity dependence of real and virtual\nphotoabsorption. The dependence of the partial cross sections on both the\nresonance helicity amplitudes and the electromagnetic multipoles is outlined.\nThe general structure of the Compton tensor is reviewed and applied to the\nspecial cases of real to real, virtual to real, and virtual to virtual Compton\nscattering. Recent theoretical developments in dispersion relations are\npresented, together with a short overview regarding static, dynamical, and\ngeneralized polarizabilities of the nucleon as well as the status of the\nGerasimov-Drell-Hearn sum rule and related integrals.", "category": "nucl-th" }, { "text": "Nuclear Lattice Simulations with Chiral Effective Field Theory: We study nuclear and neutron matter by combining chiral effective field\ntheory with non-perturbative lattice methods. In our approach nucleons and\npions are treated as point particles on a lattice. This allows us to probe\nlarger volumes, lower temperatures, and greater nuclear densities than in\nlattice QCD. The low energy interactions of these particles are governed by\nchiral effective theory and operator coefficients are determined by fitting to\nzero temperature few-body scattering data. Any dependence on the lattice\nspacing can be understood from the renormalization group and absorbed by\nrenormalizing operator coefficients. In this way we have a realistic simulation\nof many-body nuclear phenomena with no free parameters, a systematic expansion,\nand a clear theoretical connection to QCD. We present results for hot neutron\nmatter at temperatures 20 to 40 MeV and densities below twice nuclear matter\ndensity.", "category": "nucl-th" }, { "text": "Structure of eta' mesonic nuclei in a relativistic mean field theory: The structure and the energy spectrum of the $\\eta^{\\prime}$ mesonic nuclei\nare investigated in a relativistic mean field theory. One expects a substantial\nattraction for the $\\eta^{\\prime}$ meson in finite nuclei due to the partial\nrestoration of chiral symmetry in the nuclear medium. Such a hadronic scale\ninteraction for the $\\eta^{\\prime}$ mesonic nuclei may provide modification of\nthe nuclear structure. The relativistic mean field theory is a self-contained\nmodel for finite nuclei which provides the saturation property within the\nmodel, and is good to investigate the structure change of the nucleus induced\nby the $\\eta^{\\prime}$ meson. Using the local density approximation for the\nmean fields, we solve the equations of motion for the nucleons and the\n$\\eta^{\\prime}$ meson self-consistently, and obtain the nuclear density\ndistribution and the $\\eta^{\\prime}$ energy spectrum for the $\\eta^{\\prime}$\nmesonic nuclei. We take $^{12}$C, $^{16}$O and $^{40}$Ca for the target nuclei.\nWe find several bound states of the $\\eta^{\\prime}$ meson for these nuclei\nthanks to the attraction for $\\eta^{\\prime}$ in nuclei. We also find a\nsufficient change of the nuclear structure especially for the $1s$ bound state\nof $\\eta^{\\prime}$. This implies that the production of the $1s$ bound state in\nnuclear reaction may be suppressed.", "category": "nucl-th" }, { "text": "Dilepton flow and deconfinement phase transition in heavy ion collisions: The dilepton radial flow in Au+Au collisions at \\sqrt{s_{NN}}=200 GeV is\ninvestigated. The space-time evolution of the fireball is described by a 2+1\ndimensional ideal hydrodynamics with a variety of equations of state. The slope\nparameters of the transverse momentum spectra from the partonic and hadronic\nphases show distinct features and are sensitive to equation of state\nparameters. The elliptic flow and breaking of M_T scaling are also studied and\nhave distinct features for the two phases. These features can serve as clean\nsignals for the formation of a quark-gluon plasma in ultra-relativistic heavy\nion collisions.", "category": "nucl-th" }, { "text": "Collective vibrational states with fast iterative QRPA method: An iterative method we previously proposed to compute nuclear strength\nfunctions is developed to allow it to accurately calculate properties of\nindividual nuclear states. The approach is based on the\nquasi-particle-random-phase approximation (QRPA) and uses an iterative\nnon-hermitian Arnoldi diagonalization method where the QRPA matrix does not\nhave to be explicitly calculated and stored. The method gives substantial\nadvantages over conventional QRPA calculations with regards to the\ncomputational cost. The method is used to calculate excitation energies and\ndecay rates of the lowest lying 2+ and 3- states in Pb, Sn, Ni and Ca isotopes\nusing three different Skyrme interactions and a separable gaussian pairing\nforce.", "category": "nucl-th" }, { "text": "Incoherent pion photoproduction on the deuteron with polarization\n observables I: Formal expressions: Formal expressions are developed for the general five-fold differential cross\nsection of incoherent $\\pi$-photoproduction on the deuteron including beam and\ntarget polarization. The polarization observables of the cross section are\ndescribed by various beam, target and beam-target asymmetries for polarized\nphotons and/or polarized deuterons. They are given as bilinear hermitean forms\nin the reaction matrix elements divided by the unpolarized cross section. In\naddition, the corresponding observables for the semi-exclusive reaction $\\vec\nd(\\vec \\gamma,\\pi)NN$ are also given.", "category": "nucl-th" }, { "text": "Proof by characters of the orthogonal-orthogonal duality and relations\n of Casimir invariants: The theorem of orthogonal-orthogonal duality of Rowe, Repka, and Carvalho is\nproven by a method based on characters that is very different from theirs and\nakin to Helmers's half a century earlier proof of the analogous\nsympletic-symplectic duality. I demonstrate how three duality theorems listed\nby Rowe, Repka, and Carvalho allow very brief derivations of linear relations\nbetween the Casimir invariants of the connected representations based on the\ngeometry of their Young diagrams, and discuss for which physical systems other\nthan such already considered in the literature an analysis in terms of the\northogonal-orthogonal duality might be useful.", "category": "nucl-th" }, { "text": "The CSM extension for the description of positive and negative parity\n bands in even-odd nuclei: A particle-core Hamiltonian is used to describe the lowest parity partner\nbands $K^{\\pi}=1/2^{\\pm}$ in $^{237}$U and $^{239}$Pu. The quadrupole and\noctupole boson Hamiltonian associated to the core is identical to the one\npreviously used for the description of four positive and four negative parity\nbands in the neighboring even-even isotopes. The single particle space for the\nodd nucleon consists of three spherical shell model states, two of positive and\none of negative parity. The particle-core Hamiltonian consists of four terms: a\nquadrupole-quadrupole, an octupole-octupole, a spin-spin and a rotational\n$\\hat{I}^2$ interaction, with $\\hat {I}$ denoting the total angular momentum.\nThe parameters involved in the particle-core coupling Hamiltonian were fixed by\nfitting four particular energies in the two bands. The calculated excitation\nenergies are compared with the corresponding experimental data as well as with\nthose obtained with other approaches. Also, we searched for some signatures for\na static octupole deformation in the considered odd isotopes.", "category": "nucl-th" }, { "text": "Fusion and quasi-fission dynamics in nearly-symmetric reactions: Some nearly-symmetric fusion reactions are systematically investigated with\nthe improved quantum molecular dynamics (ImQMD) model. By introducing two-body\ninelastic scattering in the Fermi constraint procedure, the stability of an\nindividual nucleus and the description of fusion cross sections at energies\nnear the Coulomb barrier can be further improved. Simultaneously, the\nquasi-fission process in $^{154}$Sm+$^{160}$Gd is also investigated with the\nmicroscopic dynamics model for the first time. We find that at energies above\nthe Bass barrier, the fusion probability is smaller than $10^{-5}$ for this\nreaction, and the nuclear contact-time is generally smaller than $1500$ fm/c.\nFrom the central collisions of Sm+Gd, the neutron-rich fragments such as\n$^{164,165}$Gd, $^{192}$W can be produced in the ImQMD simulations, which\nimplies that the quasi-fission reaction could be an alternative way to\nsynthesize new neutron-rich heavy nuclei.", "category": "nucl-th" }, { "text": "Exposing the Noncollectivity in Elliptic Flow: We show that backward-forward elliptic anisotropy correlation provides an\nexperimentally accessible observable which distinguishes between collective and\nnon-collective contributions to the observed elliptic anisotropy $v_2$ in\nrelativistic heavy ion collisions. The measurement of this observable will\nreveal the momentum scale at which collective expansion seizes and where the\nelliptic anisotropy is dominated by (semi)-hard processes.", "category": "nucl-th" }, { "text": "Deuteron spin structure functions in the resonance and DIS regions: We derive relations between spin-dependent nuclear and nucleon g_1 and g_2\nstructure functions within the nuclear impulse approximation, which are valid\nat all Q^2, and in both the resonance and deep inelastic regions. We apply the\nformalism to the specific case of the deuteron, which is often used as a source\nof neutron structure information, and compare the size of the nuclear\ncorrections calculated using exact kinematics and using approximations\napplicable at large Q^2.", "category": "nucl-th" }, { "text": "Multifragmentation vs. Evaporation vs. Binary-Decay in Fragment\n Production: This paper presents part of an internal LANL Progress Report on completion of\nthe \"S\" and \"G\" versions of the improved Cascade-Exciton Model (CEM03.01) and\nthe Los Alamos Quark-Gluon String Model (LAQGSM.03.01) codes. The \"S\" versions\nconsider fragmentation of compound nuclei produced after the preequilibrium\nstage of reactions for excitation energies above 2A MeV using the Statistical\nMultifragmentation Model (SMM) by Botvina et al. (\"S\" stands for SMM), while\nthe \"G\" versions describe evaporation/fission stages of reactions using the\nfission-like binary-decay model GEMINI of Charity et al. (\"G\" stands for\nGEMINI) instead of using the the Generalized Evaporation Model GEM2 of Furihata\nincorporated into the standard versions of these codes. We present here an\nanalysis of the recent 660 MeV p + 129I and 3.65 GeV p + 112Sn JINR\nmeasurements, of the new COSY data on 1.2 GeV p + (13 nuclei from Al to Th), of\nthe 300 MeV and 1 GeV p + 56Fe data measured at GSI in inverse kinematics, and\nof the new GSI data on 1 GeV/nucleon 124Xe and 136Xe + Pb. To better understand\nthe mechanisms of fragment production, we discuss several calculated but\nnot-yet-measured kinematic characteristics of products of these reactions,\nwhich are predicted to be quite different by SMM, GEMINI, and GEM2. We find\nthese kinematic quantities to be potentially useful in differentiating these\nreaction mechanisms if they can be measured in future experiments.", "category": "nucl-th" }, { "text": "alpha decay half-lives of new superheavy nuclei within a generalized\n liquid drop model: The alpha decay half-lives of the recently produced isotopes of the 112, 114,\n116 and 118 nuclei and decay products have been calculated in the\nquasi-molecular shape path using the experimental Qalpha value and a\nGeneralized Liquid Drop Model including the proximity effects between nucleons\nin the neck or the gap between the nascent fragments. Reasonable estimates are\nobtained for the observed alpha decay half-lives. The results are compared with\ncalculations using the Density-Dependent M3Y effective interaction and the\nViola-Seaborg-Sobiczewski formulae. Generalized Liquid Drop Model predictions\nare provided for the alpha decay half-lives of other superheavy nuclei using\nthe Finite Range Droplet Model Qalpha and compared with the values derived from\nthe VSS formulae.", "category": "nucl-th" }, { "text": "Multiparticle correlations and momentum conservation in nucleus-nucleus\n collisions: Particle correlations are very actively studied in heavy-ion collisions at\nultra-relativistic energies. Here, an attempt is made at determining a proper\nreference for such studies, by taking properly into account the multiparticle\ncorrelations induced by the conservation of total momentum in the collisions.", "category": "nucl-th" }, { "text": "Pion and photon induced reactions on the nucleon in a unitary model: We present a relativistic calculation of pion scattering, pion\nphotoproduction and Compton scattering on the nucleon in the energy region of\nthe \\Del-resonance (upto 450 MeV photon lab energy), in a unified framework\nwhich obeys the unitarity constraint. It is found that the recent data on the\ncross section for nucleon Compton scattering determine accurately the\nparameters of the electromagnetic nucleon--\\Del\\ coupling. The calculated\npion-photoproduction partial-wave amplitudes agree well with the recent Arndt\nanalysis.", "category": "nucl-th" }, { "text": "Double giant dipole resonances in time-dependent density-matrix theory: The strength functions of the DGDRs in 16O and 40Ca are calculated using an\nextended version of TDHF known as the time-dependent density-matrix theory\n(TDDM). The calculations are done in a self-consistent manner, in which the\nsame Skyrme force as that used for the mean-field potential is used as the\nresidual interaction to calculate two-body correlations. It is found that the\nDGDR in 16O has a large width due to the Landau damping, although the centroid\nenergy of the DGDR is close to twice the energy of the GDR calculated in RPA.\nThe DGDR in 40Ca is found more harmonic than that in 16O.", "category": "nucl-th" }, { "text": "Potential for measurement of the tensor polarizabilities of nuclei in\n storage rings by the frozen spin method: The frozen spin method can be effectively used for a high-precision\nmeasurement of the tensor electric and magnetic polarizabilities of the\ndeuteron and other nuclei in storage rings. For the deuteron, this method would\nprovide the determination of the deuteron's polarizabilities with absolute\nprecision of order of $10^{-43}$ cm$^3$.", "category": "nucl-th" }, { "text": "On the PBF neutrino losses in superfluid cores of neutron stars: Axial anomalous contributions into neutrino PBF losses due to triplet pairing\nof neutrons are still ignored in modeling the evolution of neutron stars. In\nthis paper, the influence of the anomalous axial contributions onto the rate of\nneutron stars cooling is estimated.", "category": "nucl-th" }, { "text": "Kinetic-theory approach to low-energy collective modes in nuclei: Two different solutions of the linearized Vlasov equation for finite systems,\ncharacterized by fixed and moving-surface boundary conditions, are discussed in\na unified perspective. A condition determining the eigenfrequencies of\ncollective nuclear oscillations, that can be obtained from the moving-surface\nsolution, is studied for isoscalar vibrations of lowest multipolarity. Analytic\nexpressions for the friction and mass parameters related to the low-enegy\nsurface excitations are derived and their value is compared to values given by\nother models. Both similarities and differences are found with respect to the\nother approaches, however the close agreement obtained in many cases with one\nof the other models suggests that, in spite of some important differences, the\ntwo approaches are substantially equivalent. The formalism based on the Vlasov\nequation is more transparent since it leads to analytical expressions that can\nbe a basis for further improvement of the model.", "category": "nucl-th" }, { "text": "Strange-quark contribution to the ratio of neutral- to charged-current\n cross sections in neutrino-nucleus scattering: A formalism based on a relativistic plane wave impulse approximation is\ndeveloped to investigate the strange-quark content ($g_{A}^{s}$) of the\naxial-vector form factor of the nucleon via neutrino-nucleus scattering.\nNuclear structure effects are incorporated via an accurately calibrated\nrelativistic mean-field model. The ratio of neutral- to charged-current cross\nsections is used to examine the sensitivity of this observable to $g_{A}^{s}$.\nFor values of the incident neutrino energy in the range proposed by the FINeSSE\ncollaboration and by adopting a value of $g_{A}^{s}=-0.19$, a 30% enhancement\nin the ratio is observed relative to the $g_{A}^{s}=0$ result.", "category": "nucl-th" }, { "text": "Meson production in high-energy electron-nucleus scattering: Pseudoscalar mesons can be produced and studied in high-energy\nelectron-nucleus scattering. We review and extend our previous analysis of\nmeson production in the nuclear Coulomb field. The $P\\rightarrow \\gamma \\gamma$\ndecay rates are most directly determined for mesons produced in the\ndouble-Coulomb region where both photons are nearly real, and provided the\nbackground-hadronic contribution remains small. The larger the mass of the\nmeson the higher the electron energy needed to assure such a condition.", "category": "nucl-th" }, { "text": "$S$-factor and scattering parameters from ${}^3$He + ${}^4$He\n $\\rightarrow {}^7$Be + $\u03b3$ data: We use the next-to-leading-order (NLO) amplitude in an effective field theory\n(EFT) for ${}^3$He + ${}^4$He $\\rightarrow {}^7$Be + $\\gamma$ to perform the\nextrapolation of higher-energy data to solar energies. At this order the EFT\ndescribes the capture process using an s-wave scattering length and effective\nrange, the asymptotic behavior of $^7$Be and its excited state, and\nshort-distance contributions to the E1 capture amplitude. We use a Bayesian\nanalysis to infer the multi-dimensional posterior of these parameters from\ncapture data below 2 MeV. The total $S$-factor $S(0)= 0.578^{+0.015}_{-0.016}$\nkeV b at 68% degree of belief. We also find significant constraints on\n$^3$He-$^4$He scattering parameters.", "category": "nucl-th" }, { "text": "Baryon-to-pion ratios within generic (non)extensive statistics: The successive stages of a high-energy collision are conjectured to end up\nwith chemical and thermal freezeout of the produced particles. We utilize\ngeneric (non)extensive statistics which is believed to determine the degree of\n(non)extensivity through two critical exponents due to possible phase-space\nmodifications. This statistical approach likely manifests various types of\ncorrelations and fluctuations and also possible interactions among the\nfinal-state produced particles. We study the baryon-to-pion ratios at top RHIC\nand LHC energies including the so-called proton anomaly.", "category": "nucl-th" }, { "text": "Vacuum Structures in Hamiltonian Light-Front Dynamics: Hamiltonian light-front dynamics of quantum fields may provide a useful\napproach to systematic non-perturbative approximations to quantum field\ntheories. We investigate inequivalent Hilbert-space representations of the\nlight-front field algebra in which the stability group of the light-front is\nimplemented by unitary transformations. The Hilbert space representation of\nstates is generated by the operator algebra from the vacuum state. There is a\nlarge class of vacuum states besides the Fock vacuum which meet all the\ninvariance requirements. The light-front Hamiltonian must annihilate the vacuum\nand have a positive spectrum. We exhibit relations of the Hamiltonian to the\nnontrivial vacuum structure.", "category": "nucl-th" }, { "text": "Discussing the possibility of observation of parity violation in heavy\n ion collisions: It was recently argued that in heavy ion collision the parity could be\nbroken. This Note addresses the question of possibility of the experimental\ndetection of the effect. We discuss how parity violating effects would modify\nthe final particle distributions and how one could construct variables\nsensitive to the effect, and which measurement would be the (most) conclusive.\nDiscussing different observables we also discuss the question if the\n``signals'' can be faked by ``conventional'' effects (such as anisotropic flow,\netc.) and make estimates of the signals.", "category": "nucl-th" }, { "text": "Investigation of Level Statistics by Generalized Brody Distribution and\n Maximum Likelihood Estimation Method: With generalizing the Brody distribution to include the Poisson, GOE and GUE\nlimits and with employing the maximum likelihood estimation technique, the\nspectral statistics of different sequences were considered in the nearest\nneighbor spacing statistics framework. The ML-based estimated values for the\nparameters of generalized distribution propose more precisions in compare to\nthe predictions of other distributions. The transition in the level spacing\nstatistics of different systems were described by the distances of ML-based\npredictions for generalized distribution to three limits which determined by\nKLD measures.", "category": "nucl-th" }, { "text": "Temperature and angular momentum dependence of the quadrupole\n deformation in sd-shell: Temperature and angular momentum dependence of the quadrupole deformation is\nstudied in the middle of the sd-shell for 28Si and 27Si isotopes using the\nspherical shell model approach. The shell model calculations have been\nperformed using the standard USD interaction and the canonical partition\nfunction constructed from the calculated eigen-solutions. It is shown that the\nextracted average quadrupole moments show a transitional behavior as a function\nof temperature and the inferred transitional temperature is shown to vary with\nangular-momentum. The quadrupole deformation of the individual eigen-states is\nalso analyzed.", "category": "nucl-th" }, { "text": "Relativistic Heavy Ion Excitation of Giant Resonances: Giant resonances and giant resonances built on other giant resonances in\nnuclei are observed with very large cross sections in relativistic heavy ion\ncollisions. A theoretical effort is underway to understand the reaction\nmechanism which leads to this process, as well as a better understanding of the\nmicroscopic properties of multiphonon states, e.g., their strength, energy\ncentroids, widths and anharmonicities.", "category": "nucl-th" }, { "text": "Individual low-energy toroidal dipole state in $^{24}$Mg: The low-energy dipole excitations in $^{24}$Mg are investigated within the\nSkyrme quasiparticle random-phase-approximation (QRPA) for axial nuclei. The\ncalculations with the force SLy6 reveal a remarkable feature: the lowest\n$I^{\\pi}K=1^-1$ excitation (E = 7.92 MeV) in $^{24}$Mg is a vortical toroidal\nstate (TS) representing a specific vortex-antivortex realization of well-known\nspherical Hill's vortex in a strongly deformed axial confinement. This is a\nstriking example of an {\\it individual} TS which can be much easier\ndiscriminated in experiment than the toroidal dipole resonance embracing many\nstates. The TS acquires the lowest energy due to the huge prolate axial\ndeformation in $^{24}$Mg. The result persists for different Skyrme\nparameterizations (SLy6, SVbas, SkM*). We analyze spectroscopic properties of\nthe TS and its relation with the cluster structure of $^{24}$Mg. Similar TS\ncould exist in other highly prolate light nuclei. They could serve as promising\ntests for various reactions to probe a vortical (toroidal) nuclear flow.", "category": "nucl-th" }, { "text": "Thermodynamic Geometry of Strongly Interacting Matter: The thermodynamic geometry formalism is applied to strongly interacting\nmatter to estimate the deconfinement temperature. The curved thermodynamic\nmetric for Quantum Chromodynamics (QCD) is evaluated on the basis of lattice\ndata, whereas the hadron resonance gas model is used for the hadronic sector.\nSince the deconfinement transition is a crossover, the geometric criterion used\nto define the \\mbox{(pseudo-)critical} temperature, as a function of the\nbaryonchemical potential $\\mu_B$, is $R(T,\\mu_B)=0$, where $R$ is the scalar\ncurvature. The (pseudo-)critical temperature, $T_c$, resulting from QCD\nthermodynamic geometry is in good agreement with lattice and phenomenological\nfreeze-out temperature estimates. The crossing temperature, $T_h$, evaluated by\nthe hadron resonance gas, which suffers of some model dependence, is larger\nthan $T_c$ (about $20\\%$) signaling remnants of confinement above the\ntransition.", "category": "nucl-th" }, { "text": "Theoretical highlights of neutrino-nucleus interactions: The recent theoretical developments in the field of neutrino-nucleus\ninteractions in the few-GeV region are reviewed based on the presentations made\nat the NuInt09 Workshop. The topics of electron scattering and its connections\nwith neutrino interactions, neutrino induced quasielastic scattering and pion\nproduction (coherent and incoherent) are covered, with special emphasis on the\nchallenges that arise in the comparison with new experimental data.", "category": "nucl-th" }, { "text": "Heavy Quarkonia in the Instantaneous Bethe-Salpeter Model: The heavy quarkonia (Charmonium \\(c\\bar{c}\\) and Bottomonium \\(b\\bar{b}\\))\nare investigated in the framework of the instantaneous BS-equation (Salpeter\nequation). We parametrize confinement alternatively by a linearly rising scalar\nor a vector interaction kernel and take into account the one-gluon-exchange\n(OGE) interaction in the instantaneous approximation. Mass spectra as well as\nleptonic, two-photon, E1 and M1 decay widths are calculated. Our results show\nthat a reasonable description of the experimental data can be obtained with\nboth spin structures for the confining kernel. The relativistic treatment leads\nto an improved description compared to nonrelativistic results for the\ntwo-photon width of the \\(\\eta_c\\) and to some extent for the E1-transition\nwidths. However, characteristic deviations indicate that within a relativistic\nframework confinement is not described adequately by a potential.", "category": "nucl-th" }, { "text": "Exchange currents in octet hyperon charge radii: Octet hyperon charge radii are calculated in a chiral constituent quark model\nincluding electromagnetic exchange currents between quarks. In impulse\napproximation one observes a decrease of the hyperon charge radii with\nincreasing strangeness. This effect is reduced by exchange currents. Due to\nexchange currents, the charge radius of the negatively charged hyperons are\nclose to the proton charge radius.", "category": "nucl-th" }, { "text": "Towards modeling cluster structure of $^8$Be with chiral interaction: How the nuclear force behaves in cluster states, in particular those\nconsisting of the $\\alpha$ clusters, has been investigated so far, but not yet\nelucidated. Today the chiral effective field theory is established and it would\nshed new light on the microscopic understanding of the cluster states. We aim\nto address a possible source of the attraction in the cluster states of\n$^8\\mathrm{Be}$ in view of the pion exchange. Namely, we investigate whether\nthe two-pion-exchange interaction acts as a dominant attraction in the\n$\\alpha+\\alpha$ system as predicted by a previous work. We describe\ntheoretically the cluster structure of $^8\\mathrm{Be}$ by the Brink model, for\nwhich the effective interaction is designed from the realistic nuclear force\nderived through the chiral effective field theory. The two-body matrix elements\nof the chiral interaction with the local-Gaussian bases are formulated within\nthe approximation of the spin-isospin saturation forming an $\\alpha$ particle.\nIntroducing a global prefactor to the chiral interaction phenomenologically,\nthe ground and low-lying excited states of $^8\\mathrm{Be}$, the scattering\nphase shift of the $\\alpha$-$\\alpha$ system as well, are satisfactorily\ndepicted. The attraction in the cluster states is found to be stemming from the\ntwo-pion-exchange contributions dominantly, along with nonnegligible\nshort-range terms. The present work can be the foundation towards constructing\nrealistic cluster models, by which the cluster states will be revealed\nmicroscopically in the next step.", "category": "nucl-th" }, { "text": "RPA Correlations and Nuclear Densities in Relativistic Mean Field\n Approach: The relativistic mean field approach (RMF) is well known for describing\naccurately binding energies and nucleon distributions in atomic nuclei\nthroughout the nuclear chart. The random phase approximation (RPA) built on top\nof the RMF is also a good framework for the study of nuclear excitations. Here,\nwe examine the consequences of long range correlations brought about by the RPA\non the neutron and proton densities as given by the RMF approach.", "category": "nucl-th" }, { "text": "Can the Neutron Polarizabilities Be Determined from a Deuteron Compton\n Scattering Experiment?: A calculation of deuteron Compton scattering using non-relativistic\ndiagrammatic perturbation theory is presented, with the primary motivation of\ninvestigating the feasibility of determining the neutron polarizabilities from\nthis type of experiment. This calculation is expected to be valid for energies\nbelow 100 MeV. Previous theoretical and experimental estimates for the\npolarizabilities are given. All diagrams are calculated by expanding the photon\nwavefunctions into partial waves and using realistic deuteron wavefunctions.\nThe Green's function for the intermediate state in the dispersive states is\ndetermined numerically. Pion-exchange, relativistic, and recoil corrections are\nalso included. The low-energy theorem is shown to be satisfied. The relative\neffects of the different terms as well as their effects on the determinations\nof the polarizabilities are discussed at energies of 49, 69, and 95 MeV. The\ncross-section is dominated by the seagull, polarizability, and electromagnetic\nmultipole interactions. Relativistic and pion-exchange terms are also\nimportant, while recoil corrections and multipoles of L=2 and greater are\nnegligible. The calculation provides a reasonable description of the\nexperimental data points at 49 and 69 MeV, except for the point at the greatest\nangle. The polarizabilities are difficult to determine at these energies due to\nthe size of the experimental error bars. No data has been published at 95 MeV\nbut a more accurate determination of the polarizabilities is likely at this\nhigher energy. Detailed calculations for all terms can be found in the\nappendices.", "category": "nucl-th" }, { "text": "On the convergence of multi-channel effective interactions: A detailed analysis of convergence properties of the Andreozzi-Lee-Suzuki\niteration method, which is used for the calculation of low-momentum effective\npotentials Vlowk is presented. After summarizing different modifications of the\niteration method for one-flavor channel we introduce a simple model in order to\nstudy the generalization of the iteration method to multi-flavor channels. The\nfailure of a straightforward generalization is discussed. The introduction of a\nchannel-dependent cutoff cures the conceptual and technical problems. This\nnovel method has already been applied successfully for realistic\nhyperon-nucleon interactions.", "category": "nucl-th" }, { "text": "Recent issues in hadron spectroscopy: A brief survey is presented of recently discovered hadrons, some of them\npresumably demonstrating a new kind of internal structure. This includes :\nspin-singlet quarkonium, mesons with unexpected mass or width, baryons with two\nheavy quarks, and pentaquark candidates. Flavour configurations with a\ncombination of light and heavy quarks appear as particularly promising.", "category": "nucl-th" }, { "text": "Effects of $\u03c9$ meson self-coupling on the properties of finite\n nuclei and neutron stars: The effects of $\\omega$ meson self-coupling (OMSC) on the properties of\nfinite nuclei and neutron stars are investigated within the framework of\neffective field theory based relativistic mean-field (ERMF) model which\nincludes the contributions from all possible mixed interactions between the\nscalar-isoscalar ($\\sigma$), vector-isoscalar ($\\omega$) and vector-isovector\n($\\rho$) mesons upto the quartic order. For a realistic investigation, several\nparameter sets corresponding to different values of OMSC are generated by\nadjusting the remaining parameters of the ERMF model to fit the properties of\nthe finite nuclei. Though, all these parameter sets give equally good fit to\nthe properties of the finite nuclei, only moderate values of OMSC are favored\nfrom the \"naturalness\" point of view. The equation of state for the symmetric\nnuclear and pure neutron matters resulting from the parameter sets with the\nmoderate values of OMSC are in close agreement with the ones obtained within\nthe Dirac-Brueckner-Hartree-Fock approximation. For such parameter sets the\nlimiting mass for the neutron stars composed of $\\beta$-stable matter is $\\sim\n1.9M_\\odot$. It is found that the direct Urca process can occur in the neutron\nstars with \"canonical\" mass of $1.4M_\\odot$ only for the moderate and higher\nvalues of OMSC. Some other interesting properties for the neutron stars are\nalso discussed.", "category": "nucl-th" }, { "text": "Effective theory for the non-rigid rotor in an electromagnetic field:\n Toward accurate and precise calculations of E2 transitions in deformed nuclei: We present a model-independent approach to electric quadrupole transitions of\ndeformed nuclei. Based on an effective theory for axially symmetric systems,\nthe leading interactions with electromagnetic fields enter as minimal couplings\nto gauge potentials, while subleading corrections employ gauge-invariant\nnon-minimal couplings. This approach yields transition operators that are\nconsistent with the Hamiltonian, and the power counting of the effective theory\nprovides us with theoretical uncertainty estimates. We successfully test the\neffective theory in homonuclear molecules that exhibit a large separation of\nscales. For ground-state band transitions of rotational nuclei, the effective\ntheory describes data well within theoretical uncertainties at leading order.\nIn order to probe the theory at subleading order, data with higher precision\nwould be valuable. For transitional nuclei, next-to-leading order calculations\nand the high-precision data are consistent within the theoretical uncertainty\nestimates. We also study the faint inter-band transitions within the effective\ntheory and focus on the $E2$ transitions from the $0^+_2$ band (the \"$\\beta$\nband\") to the ground-state band. Here, the predictions from the effective\ntheory are consistent with data for several nuclei, thereby proposing a\nsolution to a long-standing challenge.", "category": "nucl-th" }, { "text": "Neutrino scattering from hydrodynamic modes in hot and dense neutron\n matter: We calculate the scattering rate of low energy neutrinos in hot and dense\nneutron matter encountered in neutrons stars and supernova in the hydrodynamic\nregime. We find that the Brillouin peak, associated with the sound mode, and\nthe Rayleigh peak, associated with the thermal diffusion mode, dominate the\ndynamic structure factor. Although the total scattering cross section is\nconstrained by the compressibility sum rule, the differential cross-section\ncalculated using the hydrodynamic response function differs from results\nobtained in approximate treatments often used in astrophysics such as random\nphase approximations (RPA). We identified these differences and discuss its\nimplications for neutrino transport in supernova.", "category": "nucl-th" }, { "text": "Studying the process $\u03b3d \\to \u03c0^0\u03b7d$: In these proceedings we present our recent results on the study of the\nprocess $\\gamma d \\to \\pi^0 \\eta d$, where the existence of a dibaryon in the\n$\\eta d$ invariant mass distribution has been recently claimed. As we will\nshow, many of the relevant aspects observed in the experiment, as the shift of\nthe $\\eta d$ and $\\pi d$ invariant mass distributions with respect to phase\nspace can be described with our model, where no dibaryon is formed. Instead, we\nconsider the interaction of the $\\gamma$ with the nucleons forming the deuteron\nto proceed through $\\gamma N \\to \\Delta(1700)\\to \\eta \\Delta(1232) \\to \\eta\n\\pi^0 N$, followed by the rescattering of the $\\pi$ and $\\eta$ with the other\nnucleon of the deuteron. Theoretical uncertainties related to different\nparameterizations of the deuteron wave function are investigated", "category": "nucl-th" }, { "text": "The hadron-quark phase transition in dense matter and neutron stars: We study the hadron-quark phase transition in the interior of neutron stars\n(NS's). We calculate the equation of state (EOS) of hadronic matter using the\nBrueckner-Bethe-Goldstone formalism with realistic two-body and three-body\nforces, as well as a relativistic mean field model. For quark matter we employ\nthe MIT bag model constraining the bag constant by using the indications coming\nfrom the recent experimental results obtained at the CERN SPS on the formation\nof a quark-gluon plasma. We find necessary to introduce a density dependent bag\nparameter, and the corresponding consistent thermodynamical formalism. We\ncalculate the structure of NS interiors with the EOS comprising both phases,\nand we find that the NS maximum masses fall in a relatively narrow interval,\n$1.4 M_\\odot \\leq M_{\\rm max} \\leq 1.7 M_\\odot$. The precise value of the\nmaximum mass turns out to be only weakly correlated with the value of the\nenergy density at the assumed transition point in nearly symmetric nuclear\nmatter.", "category": "nucl-th" }, { "text": "On three topical aspects of the N=28 isotonic chain: The evolution of single-particle orbits along the N=28 isotonic chain is\nstudied within the framework of a relativistic mean-field approximation. We\nfocus on three topical aspects of the N=28 chain: (a) the emergence of a new\nmagic number at Z=14; (b) the possible erosion of the N=28 shell; and (c) the\nweakening of the spin-orbit splitting among low-j neutron orbits. The present\nmodel supports the emergence of a robust Z=14 subshell gap in 48Ca, that\npersists as one reaches the neutron-rich isotone 42Si. Yet the proton removal\nfrom 48Ca results in a significant erosion of the N=28 shell in 42Si. Finally,\nthe removal of s1/2 protons from 48Ca causes a ~50% reduction of the spin-orbit\nsplitting among neutron p-orbitals in 42Si.", "category": "nucl-th" }, { "text": "Charge-exchange dipole excitations in neutron-rich nuclei: $-1 \\hbar\n \u03c9_0$, anti-analog pygmy, and anti-analog giant resonances: The occurrence of the low-lying charge-exchange non spin-flip dipole modes\nbelow the giant resonance in neutron-rich nuclei is predicted on the basis of\nnuclear density functional theory. The ground and excited states are described\nin the framework of the self-consistent Hartree-Fock-Bogoliubov and the\nproton-neutron quasiparticle-random-phase approximation employing a Skyrme-type\nenergy density functional. The model calculations are performed for the\nspherical neutron-rich Ca, Ni, and Sn isotopes. It is found that the low-lying\nstates appear sensitively to the shell structure associated with the $-1 \\hbar\n\\omega_0$ excitation below the Gamow-Teller states. Furthermore, the pygmy\nresonance emerges below the giant resonance when the neutrons occupy the\nlow-$\\ell (\\ell \\leq 2 -3)$ orbitals analogous to the pygmy resonance seen in\nthe electric dipole response.", "category": "nucl-th" }, { "text": "Gradient Symplectic Algorithms for Solving the Schroedinger Equation\n with Time-Dependent Potentials: We show that the method of factorizing the evolution operator to fourth order\nwith purely positive coefficients, in conjunction with Suzuki's method of\nimplementing time-ordering of operators, produces a new class of powerful\nalgorithms for solving the Schroedinger equation with time-dependent\npotentials. When applied to the Walker-Preston model of a diatomic molecule in\na strong laser field, these algorithms can have fourth order error coefficients\nthat are three orders of magnitude smaller than the Forest-Ruth algorithm using\nthe same number of Fast Fourier Transforms. When compared to the second order\nsplit-operator method, some of these algorithms can achieve comparable\nconvergent accuracy at step sizes 50 times as large. Morever, we show that\nthese algorithms belong to a one-parameter family of algorithms, and that the\nparameter can be further optimized for specific applications.", "category": "nucl-th" }, { "text": "Study of deuteron-proton charge exchange reaction at small transfer\n momentum: The charge-exchange reaction pd->npp at 1 GeV projectile proton energy is\nstudied in the multiple-scattering expansion technique. This reaction is\nconsidered in a special kinematics, when the transfer momentum from the beam\nproton to fast neutron is close to zero. The differential cross section and a\nset of polarization observables are calculated. It was shown that contribution\nof the final state interaction between two protons is very significant.", "category": "nucl-th" }, { "text": "Including off-diagonal anisotropies in anisotropic hydrodynamics: In this paper we present a method for efficiently including the effects of\noff-diagonal local rest frame momentum anisotropies in leading-order\nanisotropic hydrodynamics. The method relies on diagonalization of the\nspace-like block of the anisotropy tensor and allows one to reduce the\nnecessary moments of the distribution function in the off-diagonal case to a\nlinear combination of diagonal-anisotropy integrals. Once reduced to\ndiagonal-anisotropy integrals, the results can be computed efficiently using\ntechniques described previously in the literature. We present a general\nframework for how to accomplish this and provide examples for off-diagonal\nanisotropy moments entering into the energy-momentum tensor and viscous update\nequations which emerge when performing anisotropic pressure matching.", "category": "nucl-th" }, { "text": "Validity of the linear coupling approximation in heavy-ion fusion\n reactions at sub barrier energies: The role of higher order coupling of surface vibrations to the relative\nmotion in heavy-ion fusion reactions at near-barrier energies is investigated.\nThe coupled channels equations are solved to all orders, and also in the linear\nand the quadratic coupling approximations. Taking $^{64}$Ni + $^{92,96}$Zr\nreactions as examples, it is shown that all order couplings lead to\nconsiderably improved agreement with the experimentally measured fusion cross\nsections and average angular momenta of the compound nucleus for such heavy\nnearly symmetric systems. The importance of higher order coupling is also\nexamined for asymmetric systems like $^{16}$O + $^{112}$Cd, $^{144}$Sm, for\nwhich previous calculations of the fusion cross section seemed to indicate that\nthe linear coupling approximation was adequate. It is shown that the shape of\nthe barrier distributions and the energy dependence of the average angular\nmomentum can change significantly when the higher order couplings are included,\neven for systems where measured fusion cross sections may seem to be well\nreproduced by the linear coupling approximation.", "category": "nucl-th" }, { "text": "Hybrid stars from a constrained equation of state: We determine, within a meta-model, the properties of the nuclear matter\nequation of state (EoS) that allow for a phase transition to deconfinement\nmatter. It is shown that the properties that define the isoscalar channel are\nthe ones that are affected, in particular, a phase transition implies much\nlarger values of the skewness and kurtosis. The effect of multi-quark\ninteraction channels in the description of the quark phase in hybrid stars is\nalso studied. NS properties, such as the mass and radius of the quark core,\nshow an interplay dependence between the 8-quark vector and the 4-quark\nisovector-vector interactions. We show that low mass NS, $M\\sim 1.4 M_\\odot$,\nmay already contain a quark core, and satisfy all existing NS observational\nconstraints. We discuss the strangeness content of the quark core and its\ninfluence on the speed of sound.", "category": "nucl-th" }, { "text": "Isospin-violating nucleon-nucleon forces using the method of unitary\n transformation: Recently, we have derived the leading and subleading isospin-breaking\nthree-nucleon forces using the method of unitary transformation. In the present\nwork we extend this analysis and consider the corresponding two-nucleon forces\nusing the same approach. Certain contributions to the isospin-violating one-\nand two-pion-exchange potential have already been discussed by various groups\nwithin the effective field theory framework. Our findings agree with the\npreviously obtained results. In addition, we present the expressions for the\nsubleading charge-symmetry-breaking two-pion exchange potential which were not\nconsidered before. These corrections turn out to be numerically important.\nTogether with the three-nucleon force results presented in our previous work,\nthe results of the present study specify completely isospin-violating nuclear\nforces up to the order $q^5/\\Lambda^5$, where $q$ ($\\Lambda$) denotes the soft\n(hard) scale.", "category": "nucl-th" }, { "text": "Rho-Omega Mixing via QCD Sum Rules with Finite Mesonic Widths: Based on the analysis of both Borel and Finite-Energy QCD sum rules, the\ninclusion of finite mesonic widths leads to a dramatic effect on the\npredictions for the momentum dependence of the rho-omega mixing matrix element.\nIt is shown that the rho-omega mixing matrix element traditionally discussed in\nthe literature, has the same sign and similar magnitude in the space-like\nregion as its on-shell value. This contrasts the zero-width result where the\nmixing matrix element is typically of opposite sign in the space-like region.", "category": "nucl-th" }, { "text": "Continuum Coupling and Pair Correlation in Weakly Bound Deformed Nuclei: We formulate a new Hartree-Fock-Bogoliubov method applicable to weakly bound\ndeformed nuclei using the coordinate-space Green's function technique. An\nemphasis is put on treatment of quasiparticle states in the continuum, on which\nwe impose the correct boundary condition of the asymptotic out-going wave. We\nillustrate this method with numerical examples.", "category": "nucl-th" }, { "text": "Heavy-ion physics: freedom to do hot, dense, exciting QCD: In these two lectures I review the basics of heavy-ion collisions at\nrelativistic energies and the physics we can do with them. I aim to cover the\nbasics on the kinematics and observables in heavy-ion collider experiments, the\nbasics on the phenomenology of the nuclear matter phase diagram, some of the\nmodel building and simulations currently used in the heavy-ion physics\ncommunity and a selected list of amazing phenomenological discoveries and\npredictions.", "category": "nucl-th" }, { "text": "Statistical and Dynamic Models of Charge Balance Functions: Charge balance functions, which identify balancing particle-antiparticle\npairs on a statistical basis, have been shown to be sensitive to whether\nhadronization is delayed by several fm/c in relativistic heavy ion collisions.\nResults from two classes of models are presented here, microscopic hadronic\nmodels and thermal models. The microscopic models give results which are\ncontrary to recently published pi+pi- balance functions from the STAR\ncollaboration, whereas the thermal model roughly reproduce the experimental\nresults. This suggests that charge conservation is local at breakup, which is\nin line with expectations for a delayed hadronization. Predictions are also\npresented for balance functions binned as a function of Q_inv.", "category": "nucl-th" }, { "text": "Universal scaling of meson and baryon spectra in p-Pb collisions at 5.02\n TeV: We systematically investigate the scaling property of mesons (pions and\nkaons) and baryons (protons, ${\\rm \\Lambda}$, ${\\rm \\Xi}$ and ${\\rm \\Omega}$)\ntransverse momentum ($p_{\\rm T}$) spectra at different centrality classes\n(0-5$\\%$, 5-10$\\%$, 10-20$\\%$, 20-40$\\%$, 40-60$\\%$, 60-80$\\%$ and 80-100$\\%$)\nin proton-lead collisions with center of mass energy per nucleon pair 5.02 TeV.\nIn the low $p_{\\rm T}$ region with $p_{\\rm{T}}\\leq $ 3.9 (3.1, 2.5, 2.7, 2.4\nand 2.8) GeV/c, a universal scaling independent of the centrality is observed\nin the pion (kaon, proton, ${\\rm \\Lambda}$, ${\\rm \\Xi}$ and ${\\rm \\Omega}$)\nspectra when a dilatation, $p_{\\rm T}\\rightarrow p_{\\rm T}/K$, is applied. Here\n$K$ is a scaling parameter depending on the centrality class. We find that the\nrates at which ln$K$ changes with the logarithmic value of the average value of\nthe number of participating nucleons, ln$\\langle N_{\\rm{part}}\\rangle$, are\nstronger for baryons than those for mesons. In the high $p_{\\rm T}$ region,\nthere is a deviation from the scaling. The more peripheral the collisions are,\nthe more obvious the violation of the scaling is. In the framework of the\ncolour string percolation (CSP) model, we show that mesons and baryons are\ngenerated from the decay of clusters formed by strings overlapping in the\ntransverse plane with the same size dispersion but with different mean size.\nThe mean size of clusters for baryons is smaller than that of mesons. For the\nsame hadrons at different centrality classes, the mean size of clusters\ndecreases with the increase of centrality. The fragmentation functions for\ncluster decay are different for different hadrons, while they are universal for\nthe same hadrons at different centrality classes. The universal scaling of the\nmeson and baryon spectra in the low $p_{\\rm T}$ region can be quantitatively\nunderstood with the CSP model at the same time.", "category": "nucl-th" }, { "text": "A Monte-Carlo Approach to Zero Energy Quantum Scattering: Monte-Carlo methods for zero energy quantum scattering are developed.\nStarting from path integral representations for scattering observables, we\npresent results of numerical calculations for potential scattering and\nscattering off a schematic $^4 \\rm He $ nucleus. The convergence properties of\nMonte-Carlo algorithms for scattering systems are analyzed using stochastic\ndifferential equation as a path sampling method.", "category": "nucl-th" }, { "text": "A functional approach to nuclear electromagnetic response functions: The separated electromagnetic responses $R_L(q,\\omega)$ and $R_T(q,\\omega)$\nfor inclusive electron scattering off nuclei are studied within a functional\nscheme.", "category": "nucl-th" }, { "text": "Identifying structures in the continuum: Application to $^{16}$Be: The population and decay of two-nucleon resonances offer exciting new\nopportunities to explore dripline phenomena. The understanding of these systems\nrequires a solid description of the three-body (core+N+N) continuum. The\nidentification of a state with resonant character from the background of\nnon-resonant continuum states in the same energy range poses a theoretical\nchallenge. It is the purpose of this work to establish a robust theoretical\nframework to identify and characterize three-body resonances in a discrete\nbasis. A resonance operator is proposed, which describes the sensitivity to\nchanges in the potential. Resonances are then identified from the lowest\neigenstates of the resonance operator. The operator is diagonalized in a basis\nof Hamiltonian pseudostates, built within the hyperspherical harmonics\nformalism using the analytical THO basis. The energy and width of the resonance\nare determined from its time dependence. The method is applied to 16Be in a\n14Be+n+n model. An effective core+n potential, fitted to the available\ninformation on the subsystem 15Be, is employed. The 0+ ground state resonance\nof 16Be presents a strong dineutron configuration, which favors the picture of\na correlated two-neutron emission. Fitting the three body interaction to the\nexperimental two-neutron separation energy |S2n|=1.35(10) MeV, the computed\nwidth is Gamma(0+)=0.16 MeV. From the same Hamiltonian, a 2+ resonance is also\npredicted with E_r(2+)=2.42 MeV and Gamma(2+)=0.40 MeV. The dineutron\nconfiguration and the computed 0+ width are consistent with previous R-matrix\ncalculations for the true three-body continuum. The extracted values of the\nresonance energy and width converge with the size of the pseudostate basis and\nare robust under changes in the basis parameters. This supports the reliability\nof the method in describing the properties of unbound core+N+N systems in a\ndiscrete basis.", "category": "nucl-th" }, { "text": "Particle spectra and hydro-inspired models: Several popular parameterizations of the freeze-out conditions in\nultra-relativistic heavy-ion collisions are shortly reviewed. The common\nfeatures of the models, responsible for the successful description of hadronic\nobservables, are outlined.", "category": "nucl-th" }, { "text": "Shell-model interactions from chiral effective field theory: We construct valence-space Hamiltonians for use in shell-model calculations,\nwhere the residual two-body interaction is based on symmetry principles and the\nlow-momentum expansion from chiral effective field theory. In addition to the\nusual free-space contact interactions, we also include novel\ncenter-of-mass--dependent operators that arise due to the Galilean invariance\nbreaking by in-medium effects. We fitted the low-energy constants to 441\nground- and excited-state energies in the sd shell and obtained a\nroot-mean-square derivation of 1.8 MeV at leading order and of 0.5 MeV at\nnext-to-leading order, with natural low-energy constants in all cases. The\ndeveloped chiral shell-model interactions enable order-by-order uncertainty\nestimates and show promising predictions for neutron-rich isotopes beyond the\nfitted data set.", "category": "nucl-th" }, { "text": "Hyperon mixing and universal many-body repulsion in neutron stars: A multi-pomeron exchange potential (MPP) is proposed as a model for the\nuniversal many-body repulsion in baryonic systems on the basis of the Extended\nSoft Core (ESC) bryon-baryon interaction. The strength of MPP is determined by\nanalyzing the nucleus-nucleus scattering with the G-matrix folding model. The\ninteraction in $\\Lambda N$ channels is shown to reproduce well the experimental\n$\\Lambda$ binding energies. The equation of state (EoS) in neutron matter with\nhyperon mixing is obtained including the MPP contribution, and mass-radius\nrelations of neutron stars are derived. It is shown that the maximum mass can\nbe larger than the observed one $2M_{\\odot}$ even in the case of including\nhyperon mixing on the basis of model-parameters determined by terrestrial\nexperiments.", "category": "nucl-th" }, { "text": "Nuclear Effects in Generators: the Path Forward: The extraction of neutrino oscillation parameters requires the determination\nof the neutrino energy from observations of the hadronic final state. The use\nof nuclear targets then requires the use of event generators to isolate the\ninteresting elementary processes and to take experimental acceptances into\naccount. In this talk I briefly summarize the history of event generators and\ntheir use in nuclear physics, talk briefly about the generators used in the\nneutrino community and then discuss future necessary developments.", "category": "nucl-th" }, { "text": "VISHNU hybrid model for viscous QCD matter at RHIC and LHC energies: In this proceeding, we briefly describe the viscous hydrodynamics + hadron\ncascade hybrid model VISHNU for relativistic heavy ion collisions and report\nthe current status on extracting the QGP viscosity from elliptic flow data.", "category": "nucl-th" }, { "text": "Unitary limit and linear scaling of neutrons in harmonic trap with tuned\n CD-Bonn and square-well interactions: We study systems of finite-number neutrons in a harmonic trap at the unitary\nlimit. Two very different types of neutron-neutron interactions are applied,\nnamely, the meson-theoretic CD-Bonn potential and hard-core square-well\ninteractions, all tuned to possess infinite scattering lengths, and with\neffective ranges comparable to or larger than the trap size. The potentials are\nrenormalized to equivalent, scattering-length preserving low-momentum\npotentials, $V_{{\\rm low}-k}$, with which the particle-particle hole-hole ring\ndiagrams are summed to all orders to yield the ground-state energy $E_0$ of the\nfinite neutron system. We find the ratio $E_0/E_0^{\\rm free}$ (where $E_0^{\\rm\nfree}$ denotes the ground-state energy of the corresponding non-interacting\nsystem) to be remarkably independent from variations of the harmonic trap\nparameter, the number of neutrons, the decimation momentum of $V_{{\\rm\nlow}-k}$, and the type and effective range of the unitarity potential. Our\nresults support a special virial linear scaling relation of $E_0$. Certain\nproperties of Landau's quasi-particles for trapped neutrons at the unitary\nlimit are also discussed.", "category": "nucl-th" }, { "text": "Magnetic dipole moments as a strong signature for $\u03b1$-clustering in\n even-even self-conjugate nuclei: We investigate the magnetic dipole moments in even-even self-conjugate nuclei\nfrom ${}^{12}\\mathrm{C}$ to ${}^{44}\\mathrm{Ti}$. For the latter, the measured\ngyromagnetic factors of excited states turn out to assume the same value of $g\n\\approx + 0.5$ within statistical errors. This peculiar feature can be\ninterpreted on the basis of collective excitations of $\\alpha$-clusters.\nAnalogously, the behaviour of the same observable is studied for all isotopes\nobtained by adding one or two neutrons to the considered self-conjugate nuclei.\nIt is found that for the $N = Z + 1$ isotopes the $\\alpha$-cluster structure\nhardly contributes to the observed negative g- factor value, corroborating\nmolecular $\\alpha$-cluster models. The addition of a further neutron, however,\nrestores the original $\\alpha$-cluster g-factors, except for the semi-magic\nisotopes, in which the deviations from $g \\approx + 0.5$ can be associated with\nthe relevant shell closures. Secondly, we analyze the same observable in the\nframework of a macroscopic $\\alpha$-cluster model on a finite lattice of side\nlength $L$. We focus on the discretization effects induced in the magnetic\ndipole moments of the $2_1^+$ and the $3_1^-$ states of ${}^{12}\\mathrm{C}$ at\ndifferent values of the lattice spacing $a$.", "category": "nucl-th" }, { "text": "Compton scattering in a unitary approach with causality constraints: Pion-loop corrections for Compton scattering are calculated in a novel\napproach based on the use of dispersion relations in a formalism obeying\nunitarity. The basic framework is presented, including an application to\nCompton scattering. In the approach the effects of the non-pole contribution\narising from pion dressing are expressed in terms of (half-off-shell) form\nfactors and the nucleon self-energy. These quantities are constructed through\nthe application of dispersion integrals to the pole contribution of loop\ndiagrams, the same as those included in the calculation of the amplitudes\nthrough a K-matrix formalism. The prescription of minimal substitution is used\nto restore gauge invariance. The resulting relativistic-covariant model\ncombines constraints from unitarity, causality, and crossing symmetry.", "category": "nucl-th" }, { "text": "Bremsstrahlung Spectrum in alpha Decay: Using our previous approach to electromagnetic emission during tunneling, an\nexplicit, essentially classical, formula describing the bremsstrahlung spectrum\nin alpha decay is derived. The role of tunneling motion in photon emission is\ndiscussed. The shape of the spectrum is a universal function of the ratio Eg/Eo\n, where Eg is the photon energy and Eo is a characteristic energy depending\nonly on the nuclear charge and the energy of the alpha particle.", "category": "nucl-th" }, { "text": "N-Nucleon Effective Generators of the Poincare Group Derived from a\n Field Theory: It is shown that the ten generators of the Poincare group acting in the Fock\nspace of nucleons and mesons and based on standard Lagrangians can be\nblockdiagonalized by one and the same unitary transformation such that the\nspace of a fixed number of nucleons is separated from the rest of the Fock\nspace. The existence proof is carried through in a formal power series\nexpansion in the coupling constant to all orders. In this manner one arrives at\neffective generators of the Poincare group which act in the two subspaces\nseparately.", "category": "nucl-th" }, { "text": "Coexistence of order and chaos at critical points of first-order quantum\n phase transitions in nuclei: We study the interplay between ordered and chaotic dynamics at the critical\npoint of a generic first-order quantum phase transition in the interacting\nboson model of nuclei. Classical and quantum analyses reveal a distinct\nbehavior of the coexisting phases. While the dynamics in the deformed phase is\nrobustly regular, the spherical phase shows strongly chaotic behavior in the\nsame energy intervals. The effect of collective rotations on the dynamics is\ninvestigated.", "category": "nucl-th" }, { "text": "Approximations in Fusion and Breakup reactions induced by Radioactive\n Beams: Some commonly used approximations for complete fusion and breakup\ntransmission coefficients in collisions of weakly bound projectiles at near\nbarrier energies are assessed. We show that they strongly depend on the adopted\nclassical trajectory and can be significantly improved with proper treatment of\nthe incident and emergent currents in the WKB approximation.", "category": "nucl-th" }, { "text": "Dynamic description of ternary and quaternary splits of heavy nuclear\n systems in the deep-inelastic regime: Colliding heavy nuclear systems in the deep-inelastic regime may undergo\npartitioning into multiple fragments when fusion can not be achieved. While\nmultiple breakups are common at Fermi energy, they are rather exotic in the\ndeep-inelastic regime, where density, excitation and, in general, transport\nconditions, are expected to be different. Abundant ternary and quaternary\nsplits have been observed in recent experiments, for instance in symmetric\nsemi-central and semi-peripheral collisions with heavy systems, like\n$^{197}\\mathrm{Au}$ + $^{197}\\mathrm{Au}$ at 15 MeV per nucleon. In these\nconditions, we undertook a microscopic description of the reaction dynamics.\nRelying on the full solution of the Boltzmann-Langevin equation implemented in\nthe BLOB approach, we could follow in time the development of instabilities\nalong deformation.", "category": "nucl-th" }, { "text": "Nucleon-Nucleon Short-Range Correlations and Gribov Inelastic Shadowing\n in High Energy Hadron-Nucleus Collisions: Different types of high-energy hadron-nucleus cross sections are discussed\nemphasizing the role played by Nucleon-Nucleon (NN) Short-Range Correlations\n(SRC) and Gribov Inelastic Shadowing (IS)", "category": "nucl-th" }, { "text": "Identifying Inconsistencies in Fission Product Yield Evaluations with\n Prompt Neutron Emission: We present a self-consistency analysis of fission product yield evaluations.\nAnomalous yields are determined using a series of simple conservation checks\nand comparing charge distributions with common parameterizations. The total\nprompt neutron multiplicity as a function of product mass $\\bar{\\nu}_T(A)$ is\nderived directly from the independent fission product yields using average\ncharge conservation. This method is checked against Monte Carlo simulations of\nthe de-excitation of the fission fragments in a Hauser-Feshbach statistical\ndecay framework. The derived $\\bar{\\nu}_T(A)$ is compared with experimental\ndata, when available, and used to compare the prompt neutron multiplicity\n$\\bar{\\nu}$ for the various evaluations. Differences in $\\bar{\\nu}$ for each\nevaluation are investigated and possible sources are identified. We also\nidentify fission reactions that are inconsistent with prompt neutron data and\npropose possible solutions to remedy the observed inconsistencies.", "category": "nucl-th" }, { "text": "Nucleon mass and pion loops: Poincare' covariant Faddeev equations for the nucleon and Delta are solved to\nillustrate that an internally consistent description in terms of confined-quark\nand nonpointlike confined-diquark-correlations can be obtained. pi N-loop\ninduced self-energy corrections to the nucleon's mass are analysed and shown to\nbe independent of whether a pseudoscalar or pseudovector coupling is used.\nPhenomenological constraints suggest that this self-energy correction reduces\nthe nucleon's mass by up to several hundred MeV. That effect does not\nqualitatively alter the picture, suggested by the Faddeev equation, that\nbaryons are quark-diquark composites. However, neglecting the pi-loops leads to\na quantitative overestimate of the nucleon's axial-vector diquark component.", "category": "nucl-th" }, { "text": "Magnetic moment of the deuteron as probe of relativistic corrections: The calculation of the magnetic moment of the deuteron in the framework of\nthe Bethe--Salpeter approach is performed. The relativistic corrections are\ncalculated analytically and estimated numerically. It is shown that the main\ncontributions are due to partial waves with positive energies and $P$--waves. A\ncomparison with the non-relativistic schemes of calculations including mesonic\nexchange currents is made.", "category": "nucl-th" }, { "text": "Exotic modes of excitation in atomic nuclei far from stability: We review recent studies of the evolution of collective excitations in atomic\nnuclei far from the valley of $\\beta$-stability. Collective degrees of freedom\ngovern essential aspects of nuclear structure, and for several decades the\nstudy of collective modes such as rotations and vibrations has played a vital\nrole in our understanding of complex properties of nuclei. The multipole\nresponse of unstable nuclei and the possible occurrence of new exotic modes of\nexcitation in weakly-bound nuclear systems, present a rapidly growing field of\nresearch, but only few experimental studies of these phenomena have been\nreported so far. Valuable data on the evolution of the low-energy dipole\nresponse in unstable neutron-rich nuclei have been gathered in recent\nexperiments, but the available information is not sufficient to determine the\nnature of observed excitations. Even in stable nuclei various modes of giant\ncollective oscillations had been predicted by theory years before they were\nobserved, and for that reason it is very important to perform detailed\ntheoretical studies of the evolution of collective modes of excitation in\nnuclei far from stability. We therefore discuss the modern theoretical tools\nthat have been developed in recent years for the description of collective\nexcitations in weakly-bound nuclei. The review focuses on the applications of\nthese models to studies of the evolution of low-energy dipole modes from stable\nnuclei to systems near the particle emission threshold, to analyses of various\nisoscalar modes, those for which data are already available, as well as those\nthat could be observed in future experiments, to a description of\ncharge-exchange modes and their evolution in neutron-rich nuclei, and to\nstudies of the role of exotic low-energy modes in astrophysical processes.", "category": "nucl-th" }, { "text": "Pygmy Resonances and Neutron Skins: Motivated by a recent experiment, the distribution of electric dipole\nstrength in the neutron-rich 68Ni isotope was computed using a relativistic\nrandom phase approximation with a set of effective interactions that - although\nwell calibrated - predict significantly different values for the neutron-skin\nthickness in 208Pb. The emergence of low-energy \"Pygmy\" strength that exhausts\nabout 5-8% of the energy weighted sum rule (EWSR) is clearly identified. In\naddition to the EWSR, special emphasis is placed on the dipole polarizability.\nIn particular, our results suggest a strong correlation between the dipole\npolarizability of 68Ni and the neutron-skin thickness of 208Pb. Yet we find a\ncorrelation just as strong and an even larger sensitivity between the\nneutron-skin thickness of 208Pb and the fraction of the dipole polarizability\nexhausted by the Pygmy resonance. These findings suggest that the dipole\npolarizability may be used as a proxy for the neutron skin.", "category": "nucl-th" }, { "text": "Thermalization at lowest energies? A view from a transport model: Using the Isospin Quantum Molecular Dynamics (IQMD) model we analyzed the\nproduction of pions and kaons in the energy range of 1-2 AGeV in order to study\nthe question why thermal models could achieve a successful description. For\nthis purpose we study the variation of pion and kaon yields using different\nelementary cross sections. We show that several ratios appear to be rather\nrobust versus their variations.", "category": "nucl-th" }, { "text": "Geometrical symmetries of nuclear systems: D(3h) and T(d) symmetries in\n light nuclei: The role of discrete (or point-group) symmetries in alpha-cluster nuclei is\ndiscussed in the framework of the algebraic cluster model which describes the\nrelative motion of the alpha-particles. Particular attention is paid to the\ndiscrete symmetry of the geometric arrangement of the alpha-particles, and the\nconsequences for the structure of the corresponding rotational bands. The\nmethod is applied to study cluster states in the nuclei 12C and 16O. The\nobserved level sequences can be understood in a simple way as a consequence of\nthe underlying discrete symmetry that characterizes the geometrical\nconfiguration of the alpha-particles, i.e. an equilateral triangle with D(3h)\nsymmetry for 12C, and a tetrahedron with T(d) symmetry for 16O. The structure\nof rotational bands provides a fingerprint of the underlying geometrical\nconfiguration of alpha-particles.", "category": "nucl-th" }, { "text": "Density-functional theory for the pairing Hamiltonian: We consider the pairing Hamiltonian and systematically construct its density\nfunctional in the strong-coupling limit and in the limit of large particle\nnumber. In the former limit, the functional is an expansion into central\nmoments of occupation numbers. In the latter limit, the functional is known\nfrom BCS theory. Both functionals are nonlocal in structure, and the\nnonlocalities are in the form of simple products of local functionals. We also\nderive the relation between the occupation numbers and the Kohn-Sham density.", "category": "nucl-th" }, { "text": "Production of $a_0$-mesons in pp and pn reactions: We investigate the cross section for the reaction $NN \\to NNa_0$ near\nthreshold and at medium energies. An effective Lagrangian approach with\none-pion exchange is applied to analyze different contributions to the cross\nsection for different isospin channels. The Reggeon exchange mechanism is also\nconsidered. The results are used to calculate the contribution of the $a_0$\nmeson to the cross sections and invariant $K \\bar K$ mass distributions of the\nreactions $pp\\to pn K^+\\bar K^0$ and $pp\\to pp K^+K^-$. It is found that the\nexperimental observation of $a_0^+$ mesons in the reaction $pp\\to pn K^+\\bar\nK^0$ is much more promising than the observation of $a_0^0$ mesons in the\nreaction $pp\\to pp K^+K^-$.", "category": "nucl-th" }, { "text": "Femtometer Toroidal Structures in Nuclei: The two-nucleon density distributions in states with isospin $T=0$, spin\n$S$=1 and projection $M_S$=0 and $\\pm$1 are studied in $^2$H, $^{3,4}$He,\n$^{6,7}$Li and $^{16}$O. The equidensity surfaces for $M_S$=0 distributions are\nfound to be toroidal in shape, while those of $M_S$=$\\pm$1 have dumbbell shapes\nat large density. The dumbbell shapes are generated by rotating tori. The\ntoroidal shapes indicate that the tensor correlations have near maximal\nstrength at $r<2$ fm in all these nuclei. They provide new insights and simple\nexplanations of the structure and electromagnetic form factors of the deuteron,\nthe quasi-deuteron model, and the $dp$, $dd$ and $\\alpha d$ $L$=2 ($D$-wave)\ncomponents in $^3$He, $^4$He and $^6$Li. The toroidal distribution has a\nmaximum-density diameter of $\\sim$1 fm and a half-maximum density thickness of\n$\\sim$0.9 fm. Many realistic models of nuclear forces predict these values,\nwhich are supported by the observed electromagnetic form factors of the\ndeuteron, and also predicted by classical Skyrme effective Lagrangians, related\nto QCD in the limit of infinite colors. Due to the rather small size of this\nstructure, it could have a revealing relation to certain aspects of QCD.", "category": "nucl-th" }, { "text": "The Unified Hydrodynamics and the Pseudorapidity Distributions in Heavy\n Ion Collisions at BNL-RHIC and CERN-LHC Energies: The charged particles produced in nucleus-nucleus collisions are divided into\ntwo parts. One is from the hot and dense matter created in collisions. The\nother is from leading particles. The hot and dense matter is assumed to expand\naccording to unified hydrodynamics and freezes out into charged particles from\na space-like hypersurface with a fixed proper time of Tau_FO.The leading\nparticles are conventionally taken as the particles which inherit the quantum\nnumbers of colliding nucleons and carry off most of incident energy. The\nrapidity distributions of the charged particles from these two parts are\nformulated analytically, and a comparison is made between the theoretical\nresults and the experimental measurements performed in Au-Au and Pb-Pb\ncollisions at the respective BNL-RHIC and CERN-LHC energies. The theoretical\nresults are well consistent with experimental data.", "category": "nucl-th" }, { "text": "Onset of $\u03b7$ nuclear binding: Recent studies of $\\eta$ nuclear quasibound states by the Jerusalem-Prague\nCollaboration are reviewed, focusing on stochastic variational method self\nconsistent calculations of $\\eta$ few-nucleon systems. These calculations\nsuggest that a minimum value Re$\\,a_{\\eta N} \\approx 1$ fm (0.7 fm) is needed\nto bind $\\eta\\,^3$He ($\\eta\\,^4$He).", "category": "nucl-th" }, { "text": "Spin-dependent correlations and the semi-exclusive ^{16}O(e,e'p)\n reaction: The effect of central, tensor and spin-isospin nucleon-nucleon correlations\nupon semi-exclusive ^{16}O(e,e'p) reactions is studied for Q^2 and Bjorken x\nvalues in the range $0.2 \\lesssim Q^2 \\lesssim 1.1 (GeV/c)^2$ and 0.15\n$\\lesssim$ x $\\lesssim$ 2. The fully unfactorized calculations are performed in\na framework that accounts not only for the dynamical coupling of virtual\nphotons to correlated nucleon pairs but also for meson-exchange and\n$\\Delta_{33}$-isobar currents. Tensor correlations are observed to produce\nsubstantially larger amounts of semi-exclusive ^{16}O(e,e'p) strength than\ncentral correlations do and are predominantly manifest in the proton-neutron\nknockout channel. With the exception of the $x \\approx 2$ case, in all\nkinematical situations studied the meson-exchange and isobar currents are a\nstrong source of A(e,e'p) strength at deep missing energies. This feature gives\nthe A(e,e'p) strength at deep missing energies a pronounced transverse\ncharacter.", "category": "nucl-th" }, { "text": "Differential elliptic flow prediction at the LHC from parton transport: We predict how differential elliptic flow v2(pT) changes from RHIC to LHC\ncollision energies (Pb+Pb at 5.5 TeV/nucleon), ASSUMING that the quark-gluon\nsystem created has a ``minimal'' shear viscosity eta/s = 1/(4*pi) at both RHIC\nand the LHC.", "category": "nucl-th" }, { "text": "Predicting narrow states in the spectrum of a nucleus beyond the proton\n drip line: Properties of particle-unstable nuclei lying beyond the proton drip line can\nbe ascertained by considering those (usually known) properties of its mirror\nneutron-rich system. We have used a multi-channel algebraic scattering theory\nto map the known properties of the neutron-${}^{14}$C system to those of the\nproton-${}^{14}$O one from which we deduce that the particle-unstable\n${}^{15}$F will have a spectrum of two low lying broad resonances of positive\nparity and, at higher excitation, three narrow negative parity ones. A key\nfeature is to use coupling to Pauli-hindered states in the target.", "category": "nucl-th" }, { "text": "Enhancement of deuteron production in jets: A strong enhancement of deuteron production in jets has been recently\nobserved in proton-proton collisions at LHC. We show that the effect is due to\ntwo independent factors: a collimation of jet nucleons and a smallness of\nnucleon source. The coalescence parameter of jet deuterons is shown to acquire\nits maximal possible value.", "category": "nucl-th" }, { "text": "Dynamical Model of Coherent Pion Production in Neutrino-Nucleus\n Scattering: We study coherent pion production in neutrino-nucleus scattering in the\nenergy region relevant to neutrino oscillation experiments of current interest.\nOur approach is based on a combined use of the Sato-Lee model of electroweak\npion production on a nucleon and the Delta-hole model of pion-nucleus\nreactions. Thus we develop a model which describes pion-nucleus scattering and\nelectroweak coherent pion production in a unified manner. Numerical\ncalculations are carried out for the case of the 12C target. All the free\nparameters in our model are fixed by fitting to both total and elastic\ndifferential cross sections for pi-12C scattering. Then we demonstrate the\nreliability of our approach by confronting our prediction for the coherent pion\nphoto-productions with data. Finally, we calculate total and differential cross\nsections for neutrino-induced coherent pion production, and some of the results\nare (will be) compared with the recent (forthcoming) data from K2K, SciBooNE\nand MiniBooNE. We also study effect of the non-locality of the\nDelta-propagation in the nucleus, and compare the elementary amplitudes used in\ndifferent microscopic calculations.", "category": "nucl-th" }, { "text": "Antiproton-nucleus electromagnetic annihilation as a way to access the\n proton timelike form factors: Contrary to the reaction pbar + p --> e+ e- with a high momentum incident\nantiproton on a free target proton at rest, in which the invariant mass M of\nthe (e+ e-) pair is necessarily much larger than the (pbar p) mass, in the\nreaction pbar + d --> n e+ e- the value of M can take values near or below the\n(pbar p) mass. In the antiproton-deuteron electromagnetic annihilation, this\nallows to access the proton electromagnetic form factors in the time-like\nregion of q^2 near the (pbar p) threshold. We estimate the cross section\ndsigma(pbar +d --> e+ e- n)/dM for an antiproton beam momentum of 1.5 GeV/c. We\nfind that near the (pbar p) threshold this cross section is about 1 pb/MeV. The\ncase of heavy nuclei target is also discussed. Elements of experimental\nfeasibility are presented for the process pbar + d --> n e+ e- in the context\nof the Panda project.", "category": "nucl-th" }, { "text": "Bounding the ground-state energy of a many-body system with the\n differential method: This paper promotes the differential method as a new fruitful strategy for\nestimating a ground-state energy of a many-body system. The case of an\narbitrary number of attractive Coulombian particles is specifically studied and\nwe make some favorable comparison of the differential method to the existing\napproaches that rely on variational principles. A bird's-eye view of the\ntreatment of more general interactions is also given.", "category": "nucl-th" }, { "text": "Nuclear Scission and Quantum Localization: We examine nuclear scission within a fully quantum-mechanical microscopic\nframework, focusing on the non-local aspects of the theory. Using\n$^{240}\\textrm{Pu}$ hot fission as an example, we discuss the identification of\nthe fragments and the calculation of their kinetic, excitation, and interaction\nenergies, through the localization of the orbital wave functions. We show that\nthe \"disentanglement\" of the fragment wave functions is essential to the\nquantum-mechanical definition of scission and the calculation of physical\nobservables. Finally, we discuss the fragments' pre-scission excitation\nmechanisms and give a non-adiabatic description of their evolution beyond\nscission.", "category": "nucl-th" }, { "text": "v4 from ideal and viscous hydrodynamic simulations of nuclear collisions\n at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron\n Collider (LHC): We compute v4/(v2)^2 in ideal and viscous hydrodynamics. We investigate its\nsensitivity to details of the hydrodynamic model and compare the results to\nexperimental data from RHIC. Whereas v2 has a significant sensitivity only to\ninitial eccentricity and viscosity while being insensitive to freeze out\ntemperature, we find that v4/(v2)^2 is quite insensitive to initial\neccentricity. On the other hand, it can still be sensitive to shear viscosity\nin addition to freeze out temperature, although viscous effects do not\nuniversally increase v4/(v2)^2 as originally predicted. Consistent with data,\nwe find no dependence on particle species. We also make a prediction for\nv4/(v2)^2 in heavy ion collisions at the LHC.", "category": "nucl-th" }, { "text": "Superscaling of Inclusive Electron Scattering from Nuclei: We investigate the degree to which the concept of superscaling, initially\ndeveloped within the framework of the relativistic Fermi gas model, applies to\ninclusive electron scattering from nuclei. We find that data obtained from the\nlow energy loss side of the quasielastic peak exhibit the superscaling\nproperty, i.e., the scaling functions f(\\psi') are not only independent of\nmomentum transfer (the usual type of scaling: scaling of the first kind), but\ncoincide for A \\geq 4 when plotted versus a dimensionless scaling variable\n\\psi' (scaling of the second kind). We use this behavior to study as yet poorly\nunderstood properties of the inclusive response at large electron energy loss.", "category": "nucl-th" }, { "text": "On Probabilities of E2 Transitions between Positive-Parity States in\n ^160Dy Nucleus: Reduced probabilities B(E2) of \\gamma transitions between states of positive\nparity in the ^160Dy nucleus are calculated within the framework of the\ninteracting boson model (IBM-1). The results are compared with the experimental\ndata.", "category": "nucl-th" }, { "text": "Initial Conditions for Modified DGLAP Evolution of the Modified\n Fragmentation Functions in Nuclear Medium: Initial conditions are required to solve medium modified DGLAP (mDGLAP)\nevolution equations for modified fragmentation functions due to multiple\nscatterings and parton energy loss. Such initial conditions should in principle\ninclude energy loss for partons at scale $Q_0$ above which mDGLAP evolution\nequations can be applied. Several models for the initial condition motivated by\ninduced gluon bremsstrahlung in perturbative QCD are used to calculate the\nmodified fragmentation functions in nuclear medium and to extract the jet\ntransport parameter $\\hat q$ from fits to experimental data in deeply inelastic\nscattering (DIS) off nuclei. The model with a Poisson convolution of multiple\ngluon emissions is found to provide the overall best $\\chi^2$/d.o.f. fit to the\nHERMES data and gives a value of $\\hat q_0 \\approx 0.020 \\pm 0.005$ GeV$^2$/fm\nat the center of a large nucleus.", "category": "nucl-th" }, { "text": "A Reanalysis of Single Photon Data at CERN SPS: We reanalyze the WA98 single photon data at CERN SPS by incorporating several\nrecent developments in the study of prompt and thermal photon production from\nrelativistic heavy ion collisions. Isospin and shadowing corrected NLO pQCD,\nalong with an optimized scale for factorization, fragmentation and\nrenormalization are considered for prompt photon production. Photons from\nthermal medium are estimated by considering a boost invariant azimuthally\nanisotropic hydrodynamic expansion of the plasma along with a well tested\nequation of state and initial conditions. A quantitative explanation of the\ndata is obtained by combining $\\kappa \\times$ prompt with thermal photons,\nwhere $\\kappa$ is an overall scaling factor. We show that, elliptic flow of\nthermal photons can play a crucial role to distinguish between the `with' and\n`without' phase transition scenarios at SPS energy.", "category": "nucl-th" }, { "text": "Thermal Effects for Quark and Gluon Distributions in Heavy-Ion\n Collisions: In-medium effects for distributions of quarks and gluons in central A+A\ncollisions are considered. We suggest a duality principle, which means\nsimilarity of thermal spectra of hadrons produced in heavy-ion collisions and\ninclusive spectra which can be obtained within the dynamic quantum scattering\ntheory. Within the suggested approach we show that the mean square of the\ntransverse momentum for these partons grows and then saturates when the initial\nenergy increases. It leads to the energy dependence of hadron transverse mass\nspectra which is similar to that observed in heavy ion collisions.", "category": "nucl-th" }, { "text": "Symmetry energy and nucleon-nucleon cross sections: The extension of the Boltzmann-Uehling-Uhlenbeck model of nucleus-nucleus\ncollision is presented. The isospin-dependent nucleon-nucleon cross sections\nare estimated using the proper volume extracted from the equation of state of\nthe nuclear matter transformed into the form of the Van der Waals equation of\nstate. The results of such simulations demonstrate the dependence on symmetry\nenergy which typically varies strongly from the results obtained using only the\nisospin-dependent mean-field. The evolution of the n/p multiplicity ratio with\nangle and kinetic energy, in combination with the elliptic flow of neutrons and\nprotons, provides a suitable set of observables for determination of the\ndensity dependence of the symmetry energy. The model thus provides an\nenvironment for testing of equations of state, used for various applications in\nnuclear physics and astrophysics.", "category": "nucl-th" }, { "text": "Symmetry Energy II: Isobaric Analog States: Using excitation energies to isobaric analog states (IAS) and charge\ninvariance, we extract nuclear symmetry coefficients, from a mass formula, on a\nnucleus-by-nucleus basis. Consistently with charge invariance, the coefficients\nvary weakly across an isobaric chain. However, they change strongly with\nnuclear mass and range from a_a~10 MeV at mass A~10 to a_a~22 MeV at A~240.\nFollowing the considerations of a Hohenberg-Kohn functional for nuclear\nsystems, we determine how to find in practice the symmetry coefficient using\nneutron and proton densities, even when those densities are simultaneously\naffected by significant symmetry-energy and Coulomb effects. These results\nfacilitate extracting the symmetry coefficients from Skyrme-Hartree-Fock (SHF)\ncalculations, that we carry out using a variety of Skyrme parametrizations in\nthe literature. For the parametrizations, we catalog novel short-wavelength\ninstabilities. In comparing the SHF and IAS results for the symmetry\ncoefficients, we arrive at narrow (+-2.4 MeV) constraints on the symmetry\nenergy values S(rho) at 0.04 1.6 fm^{-1}. It is therefore likely that the effect of\nthree-nucleon interactions on 1S0 superfluidity is small at the BCS level. The\ncharge dependence of nuclear interactions has a 10% effect on the pairing gap.", "category": "nucl-th" }, { "text": "Mean field effects in heavy-ion collisions at AGS energies: The question whether mean field effects exist in heavy-ion collisions at AGS\nenergies is studied in the framework of A Relativistic Transport (ART) model.\nIt is found that in central collisions of Au+Au at $P_{beam}/A=$11.6 GeV/c a\nsimple, Skyrme-type nuclear mean field satisfying the causality requirement\nreduces the maximum baryon and energy densities reached in the cascade model by\nabout 30\\% and 40\\%, respectively. The mean field affects the inclusive, single\nparticle observables of various hadrons by at most 20\\%. We show, however, that\nthe mean field causes a factor of 2.5 increase in the strength of the baryon\ntransverse collective flow.", "category": "nucl-th" }, { "text": "Relativistic Effects in Electroweak Nuclear Responses: The electroweak response functions for inclusive electron scattering are\ncalculated in the Relativistic Fermi Gas model, both in the quasi-elastic and\nin the $\\Delta$ peak regions. The impact of relativistic kinematics at high\nmomentum transfer is investigated through an expansion in the initial nucleonic\nmomentum, which is however exact in the four-momentum of the exchanged boson.\nThe same expansion is applied to the meson exchange currents in the\nparticle-hole sector: it is shown that the non-relativistic currents can be\ncorrected by simple kinematical factors to account for relativity. The\nleft-right asymmetry measured via polarized electron scattering is finally\nevaluated in the quasi-elastic and $\\Delta$ peaks.", "category": "nucl-th" }, { "text": "The quark condensate in relativistic nucleus-nucleus collisions: We compute the modification of the quark condensate $<\\bar{q} q>$ in\nrelativistic nucleus-nucleus collisions and estimate the 4-volume, where the\nquark condensate is small ($<\\bar{q}q>/<\\bar{q} q>_0\\leq$ 0.1--0.3) using\nhadron phase-space distributions obtained with the quark-gluon string model. As\na function of the beam energy the 4-volume rises sharply at a beam energy\n$E_{lab}/A \\simeq$ (2--5) GeV, remains roughly constant up to beam energies\n$\\simeq 20$ GeV and rises at higher energies. At low energies the reduction of\nthe condensate is mainly due to baryons, while at higher energies the rise of\nthe 4-volume is due to the abundant mesons produced. Based on our results we\nexpect that moderate beam energies on the order of 10 GeV per nucleon are\nfavourable for studying the restoration of chiral symmetry in a baryon-rich\nenvironment in nucleus-nucleus collisions.", "category": "nucl-th" }, { "text": "Study of fusion dynamics using Skyrme energy density formalism with\n different surface corrections: Within the framework of Skyrme energy density formalism, we investigate the\nrole of surface corrections on the fusion of colliding nuclei. For this, the\ncoefficient of surface correction was varied between 1/36 and 4/36, and its\nimpact was studied on about 180 reactions. Our detailed investigations indicate\na linear relationship between the fusion barrier heights and strength of the\nsurface corrections. Our analysis of the fusion barriers advocate the strength\nof surface correction of 1/36.", "category": "nucl-th" }, { "text": "Phase Variation of Hadronic Amplitudes: The phase variation with angle of hadronic amplitudes is studied with a view\nto understanding the underlying physical quantities which control it and how\nwell it can be determined in free space. We find that unitarity forces a\nmoderately accurate determination of the phase in standard amplitude analyses\nbut that the nucleon-nucleon analyses done to date do not give the phase\nvariation needed to achieve a good representation of the data in multiple\nscattering calculations. Models are examined which suggest its behavior near\nforward angles is related to the radii of the real and absorptive parts of the\ninteraction. The dependence of this phase on model parameters is such that if\nthese radii are modified in the nuclear medium (in combination with the change\ndue to the shift in energy of the effective amplitude in the medium) then the\nlarger magnitudes of the phase needed to fit the data might be attainable, but\nonly for negative values of the phase variation parameter.", "category": "nucl-th" }, { "text": "Effects of the ground state correlations on the structure of vibrational\n states: A method to treat the ground state correlations beyond the RPA is presented.\nA set of nonlinear equations taking into account effects of the ground state\ncorrelations on the pairing and phonon-phonon coupling is derived. The\ninfluence of such correlations on properties of the vibrational states in\nspherical nuclei is studied.", "category": "nucl-th" }, { "text": "Note on neutron star equation of state in the light of GW170817: From the very first multimessenger event of GW170817, clean robust\nconstraints can be obtained for the tidal deformabilities of the two stars\ninvolved in the merger, which provides us unique opportunity to study the\nequation of states (EOSs) of dense stellar matter. In this contribution, we\nemploy a model from the quark level, describing consistently a nucleon and\nmany-body nucleonic system from a quark potential. We check that our sets of\nEOSs are consistent with available experimental and observational constraints\nat both sub-nuclear saturation densities and higher densities. The agreements\nwith ab-initio calculations are also good. Especially, we tune the density\ndependence of the symmetry energy (characterized by its slope at nuclear\nsaturation $L$) and study its influence on the tidal deformability. The\nso-called $QMF18$ EOS is named after the case of $L=40~\\rm MeV$, and it gives\n$M_{\\rm TOV} =2.08~M_\\odot$ and $R= 11.77~\\rm km$, $\\Lambda=331$ for a\n$1.4\\,M_\\odot$ star. The tidal signals are demonstrated to be insensitive to\nthe uncertain crust-core matching, despite the good correlation between the\nsymmetry energy slope and the radius of the star.", "category": "nucl-th" }, { "text": "Two-photon exchange effect on deuteron electromagnetic form factors: Corrections of two-photon exchange to proton and neutron electromagnetic form\nfactors are employed to study the effect of two-photon exchange on the deuteron\nelectromagnetic form factors. Numerical results of the effect are given. It is\nsuggested to test the effect in the measurement of $P_z$ in a small angle\nlimit.", "category": "nucl-th" }, { "text": "Description of shape coexistence in $^{96}$Zr based on the collective\n quadrupole Bohr Hamiltonian: Experimental data on $^{96}$Zr indicate coexisting spherical and deformed\nstructures with small mixing amplitudes. We investigate the properties of the\nlow-lying collective states of $^{96}$Zr based on the collective quadrupole\nBohr Hamiltonian. The $\\beta$-dependent collective potential having two minima\n-- spherical and deformed, is fixed so to describe experimental data in the\nbest way.Good agreement with the experimental data on the excitation energies,\n$B(E2)$ and $B(M1)$ reduced transition probabilities is obtained. It is shown\nthat the low-energy structure of $^{96}$Zr can be reproduced in a satisfactory\nway in the geometrical model with a potential function supporting shape\ncoexistence. However, the excitation energy of the $2^+_2$ state can be\nreproduced only if the rotation inertia coefficient is taken five times smaller\nthen the vibrational one in the region of the deformed well. It is shown also\nthat shell effects are important for the description of the $B(M1;2^+_2\n\\rightarrow 2^+_1)$ value. An indication on the influence of the pairing\nvibrational mode on the $\\rho^2 (0^+_2 \\rightarrow 0^+_1)$ value is obtained.", "category": "nucl-th" }, { "text": "Pairing, quasi-spin and seniority: We present our concise notes for the lectures and tutorials on pairing,\nquasi-spin and seniority delivered at SERB school on Role of Symmetries in\nNuclear Physics, AMITY University, $2019$. Starting with some generic features\nof residual nucleon-nucleon interactions, we provide detailed derivation of the\nmatrix elements for the $\\delta$-interaction which is the basis for the\nstandard pairing Hamiltonian. The eigen values for standard pairing Hamiltonian\nare then obtained within the quasi-spin formalism. The algebra involving\nquasi-spin operators is performed explicitly using the annihilation and\ncreation operators for single nucleon together with the application of Wicks\ntheorem. These techniques are expected to be helpful in deriving the mean-field\nequations for the $Hartree-Fock$, $Bardeen-Cooper-Schrieffer$ and\n$Hartree-Fock$ Bogoliubov theories.", "category": "nucl-th" }, { "text": "Spectator induced electromagnetic effects in heavy-ion collisions and\n space-time-momentum conditions for pion emission: We present our calculation of electromagnetic effects, induced by the\nspectator charge on Feynman-$x_F$ distributions of charged pions in peripheral\n$Pb+Pb$ collisions at CERN SPS energies, including realistic initial\nspace-time-momentum conditions for pion emission. The calculation is performed\nin the framework of our simplified implementation of the fire-streak model,\nadopted to the production of both $\\pi^-$ and $\\pi^+$ mesons. Isospin effects\nare included to take into account the asymmetry in production of $\\pi^+$ and\n$\\pi^-$ at high rapidity. A comparison to a simpler model from the literature\nis made. We obtain a good description of the NA49 data on the $x_F$- and\n$p_T$-dependence of the ratio of cross sections $\\pi^+/\\pi^-$. The experimental\ndata favors short times ($0.5<\\tau<2$~fm/$c$) for fast pion creation in the\nlocal fire-streak rest frame. The possibility of the expansion of the\nspectators is considered in our calculation, and its influence on the\nelectromagnetic effect observed for the $\\pi^+/\\pi^-$ ratio is discussed. In\naddition we discuss the relation between anisotropic flow and the\nelectromagnetic distortion of $\\pi^+/\\pi^-$ ratios, and study the influence of\ntransverse expansion of fire streaks as well as their vorticity on this\ndistortion. In this latter study we find that inclusion of rotation of fire\nstreaks in our model gives a satisfactory description of the rapidity\ndependence of pion directed flow. We conclude that {our implementation of the}\nfire-streak model, which properly describes the centrality dependence of\n$\\pi^-$ rapidity spectra at CERN SPS energies, also provides a quantitative\ndescription of the electromagnetic effect on the $\\pi^+/\\pi^-$ ratio as a\nfunction of $x_F$.", "category": "nucl-th" }, { "text": "Octet Spin Fractions and the Proton Spin Problem: The relatively small fraction of the spin of the proton carried by its quarks\npresents a major challenge to our understanding of the strong interaction.\nTraditional efforts to explore this problem have involved new and imaginative\nexperiments and QCD based studies of the nucleon. We propose a new approach to\nthe problem which exploits recent advances in lattice QCD. In particular, we\nextract values for the spin carried by the quarks in other members of the\nbaryon octet in order to see whether the suppression observed for the proton is\na general property or depends significantly on the baryon structure. We compare\nthese results with the values for the spin fractions calculated within a model\nthat includes the effects of confinement, relativity, gluon exchange currents\nand the meson cloud required by chiral symmetry, finding a very satisfactory\nlevel of agreement given the precision currently attainable.", "category": "nucl-th" }, { "text": "Estimates of hyperon polarization in heavy-ion collisions at collision\n energies $\\sqrt{s_{NN}}=$ 4--40 GeV: Global polarization of $\\Lambda$ and $\\bar{\\Lambda}$ hyperons in Au+Au\ncollisions at collision energies $\\sqrt{s_{NN}}=$ 4-40 GeV in the midrapidity\nregion and total polarization, i.e. averaged over all rapidities, are studied\nwithin the scope of the thermodynamical approach. The relevant vorticity is\nsimulated within the model of the three-fluid dynamics (3FD). It is found that\nthe performed rough estimate of the global midrapidity polarization quite\nsatisfactorily reproduces the experimental STAR data on the polarization,\nespecially its collision-energy dependence. The total polarization increases\nwith the collision energy rise, which is in contrast to the decrease of the\nmidrapidity polarization. This suggests that at high collision energies the\npolarization reaches high values in fragmentation regions.", "category": "nucl-th" }, { "text": "The nuclear fusion reaction rate based on relativistic equilibrium\n velocity distribution: The Coulomb barrier is in general much higher than thermal energy. Nuclear\nfusion reactions occur only among few protons and nuclei with higher relative\nenergies than Coulomb barrier. It is the equilibrium velocity distribution of\nthese high-energy protons and nuclei that participates in determining the rate\nof nuclear fusion reactions. In the circumstance it is inappropriate to use the\nMaxwellian velocity distribution for calculating the nuclear fusion reaction\nrate. We use the relativistic equilibrium velocity distribution for this\npurpose. The rate based on the relativistic equilibrium velocity distribution\nhas a reduction factor with respect to that based on the Maxwellian\ndistribution, which factor depends on the temperature, reduced mass and atomic\nnumbers of the studied nuclear fusion reactions. This signifies much to the\nsolar neutrino problem.", "category": "nucl-th" }, { "text": "Probing the symmetry energy and the degree of isospin equilibrium: The rapidity dependence of the single- and double- neutron to proton ratios\nof nucleon emission from isospin-asymmetric but mass-symmetric reactions Zr+Ru\nand Ru+Zr at energy range $100 \\sim 800$ A MeV and impact parameter range\n$0\\sim 8$ fm is investigated. The reaction system with isospin-asymmetry and\nmass-symmetry has the advantage of simultaneously showing up the dependence on\nthe symmetry energy and the degree of the isospin equilibrium. We find that the\nbeam energy- and the impact parameter dependence of the slope parameter of the\ndouble neutron to proton ratio ($F_D$) as function of rapidity are quite\nsensitive to the density dependence of symmetry energy, especially at energies\n$E_b\\sim 400$ A MeV and reduced impact parameters around 0.5. Here the symmetry\nenergy effect on the $F_D$ is enhanced, as compared to the single neutron to\nproton ratio. The degree of the equilibrium with respect to isospin (isospin\nmixing) in terms of the $F_D$ is addressed and its dependence on the symmetry\nenergy is also discussed.", "category": "nucl-th" }, { "text": "Soliton propagation in relativistic hydrodynamics: We study the conditions for the formation and propagation of Korteweg-de\nVries (KdV) solitons in nuclear matter. In a previous work we have derived a\nKdV equation from Euler and continuity equations in non-relativistic\nhydrodynamics. In the present contribution we extend our formalism to\nrelativistic fluids. We present results for a given equation of state, which is\nbased on quantum hadrodynamics (QHD).", "category": "nucl-th" }, { "text": "Thermalization through parton transport: A radiative transport model is used to study kinetic equilibration during the\nearly stage of a relativistic heavy ion collision. The parton system is found\nto be able to overcome expansion and move toward thermalization via parton\ncollisions. Scaling behaviors show up in both the pressure anisotropy and the\nenergy density evolutions. In particular, the pressure anisotropy evolution\nshows an approximate alpha_s scaling when radiative processes are included. It\napproaches an asymptotic time evolution on a time scale of 1 to 2 fm/c. The\nenergy density evolution shows an asymptotic time evolution that decreases\nslower than the ideal hydro evolution. These observations indicate that partial\nthermalization can be achieved and viscosity is important for the evolution\nduring the early longitudinal expansion stage of a relativistic heavy ion\ncollision.", "category": "nucl-th" }, { "text": "Pairing-induced speedup of nuclear spontaneous fission: Collective inertia is strongly influenced at the level crossing at which\nquantum system changes diabatically its microscopic configuration. Pairing\ncorrelations tend to make the large-amplitude nuclear collective motion more\nadiabatic by reducing the effect of those configuration changes. Competition\nbetween pairing and level crossing is thus expected to have a profound impact\non spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on\nspontaneous fission, we study the dynamic fission trajectories of $^{264}$Fm\nand $^{240}$Pu using the state-of-the-art self-consistent framework. We employ\nthe superfluid nuclear density functional theory with the Skyrme energy density\nfunctional SkM$^*$ and a density-dependent pairing interaction. Along with\nshape variables, proton and neutron pairing correlations are taken as\ncollective coordinates. The collective inertia tensor is calculated within the\nnonperturbative cranking approximation. The fission paths are obtained by using\nthe least action principle in a four-dimensional collective space of shape and\npairing coordinates. Pairing correlations are enhanced along the minimum-action\nfission path. For the symmetric fission of $^{264}$Fm, where the effect of\ntriaxiality on the fission barrier is large, the geometry of fission pathway in\nthe space of shape degrees of freedom is weakly impacted by pairing. This is\nnot the case for $^{240}$Pu where pairing fluctuations restore the axial\nsymmetry of the dynamic fission trajectory. The minimum-action fission path is\nstrongly impacted by nucleonic pairing. In some cases, the dynamical coupling\nbetween shape and pairing degrees of freedom can lead to a dramatic departure\nfrom the static picture. Consequently, in the dynamical description of nuclear\nfission, particle-particle correlations should be considered on the same\nfooting as those associated with shape degrees of freedom.", "category": "nucl-th" }, { "text": "Kaon-nucleon scattering to one-loop order in heavy baryon chiral\n perturbation theory: We calculate the T-matrices of kaon-nucleon ($KN$) and antikaon-nucleon\n($\\overline{K}N$) scattering to one-loop order in SU(3) heavy baryon chiral\nperturbation theory (HB$\\chi$PT). The low-energy constants (LECs) and their\ncombinations are then determined by fitting the phase shifts of $KN$ scattering\nand the corresponding data. This leads to a good description of the phase\nshifts below 200 MeV kaon laboratory momentum. We obtain the LEC uncertainties\nthrough statistical regression analysis. We also determine the LECs through the\nuse of scattering lengths in order to check the consistency of the HB$\\chi$PT\nframework for different observables and obtain a consistent result. By using\nthese LECs, we predict the $\\overline{K}N$ elastic scattering phase shifts and\nobtain reasonable results. The scattering lengths are also predicted, which\nturn out to be in good agreement with the empirical values except for the\nisospin-0 $\\overline{K}N$ scattering length that is strongly affected by the\n$\\Lambda(1405)$ resonance. As most calculations in the chiral perturbation\ntheory, the convergence issue is discussed in detail. Our calculations provide\na possibility to investigate the baryon-baryon interaction in HB$\\chi$PT.", "category": "nucl-th" }, { "text": "Revisiting an extended-mean-field approach in heavy-ion collisions\n around the Fermi energy: Static and dynamical aspects of nuclear systems are described through an\nextended time-dependent mean-field approach. The foundations of the formalism\nare presented, with highlights on the estimation of average values and their\ncorresponding dispersions. In contrast to semiclassical transport models, the\nparticular interest of this description lies on its intrinsic quantal\ncharacter. The reliability of this approach is discussed by means of\nstopping-sensitive observables analysis in heavy-ion collisions in the range of\n20 to 120 MeV per nucleon.", "category": "nucl-th" }, { "text": "Di-neutron correlation and soft dipole excitation in medium mass\n neutron-rich nuclei near drip-line: The neutron pairing correlation and the soft dipole excitation in medium-mass\nnuclei near drip-line are investigated from a viewpoint of the di-neutron\ncorrelation. Numerical analyses by means of the coordinate-space HFB and the\ncontinuum QRPA methods are performed for even-even $^{18-24}$O, $^{50-58}$Ca\nand $^{80-86}$Ni. A clear signature of the di-neutron correlation is found in\nthe HFB ground state; two neutrons are correlated at short relative distances\n$\\lesim 2$ fm with large probability $\\sim 50%$. The soft dipole excitation is\ninfluenced strongly by the neutron pairing correlation, and it accompanies a\nlarge transition density for pair motion of neutrons. This behavior originates\nfrom a coherent superposition of two-quasiparticle configurations $[l\\times\n(l+1)]_{L=1}$ consisting of continuum states with high orbital angular momenta\n$l$ reaching an order of $l\\sim 10$. It raises a picture that the soft dipole\nexcitation under the influence of neutron pairing is characterized by motion of\ndi-neutron in the nuclear exterior against the remaining $A-2$ subsystem.\nSensitivity to the density dependence of effective pair force is discussed.", "category": "nucl-th" }, { "text": "What hard probes tell us about the quark-gluon plasma: Theory: In the study of the quark-gluon plasma in high-energy heavy-ion collisions,\nhard and electromagnetic (EM) processes play an essential role as probes of the\nproperties of the dense medium. They can be used to study a wide range of\nproperties of the dense medium in high-energy heavy-ion collisions, from\nspace-time profiles of the dense matter, bulk transport coefficients to EM\nresponses and the jet transport parameter. I review in this talk these medium\nproperties, how they can be studied through hard and EM probes and the status\nof recent theoretical and phenomenological investigations.", "category": "nucl-th" }, { "text": "Intermediate-Energy Semileptonic Probes of the Hadronic Neutral Current: The present and future prospects of intermediate-energy semileptonic neutral\ncurrent studies are reviewed. Possibilities for using neutrino and\nparity-violating electron scattering from nucleons and nuclei to study hadron\nstructure and nuclear dynamics are emphasized, with particular attention paid\nto probes of the nucleon's strangeness content. Connections are drawn between\nsuch studies and tests of electroweak gauge theory using electron or neutrino\nscattering. Outstanding theoretical issues in the interpretation of\nsemileptonic neutral current measurements are highlighted, and the prospects\nfor undertaking neutrino and parity-violating electron scattering experiments\nin the near future are surveyed.", "category": "nucl-th" }, { "text": "Influence of the hadronic equation of state on the hadron-quark phase\n transition in neutron stars: We study the hadron-quark phase transition in the interior of neutron stars.\nThe relativistic mean field (RMF) theory is adopted to describe the hadronic\nmatter phase, while the Nambu-Jona-Lasinio (NJL) model is used for the quark\nmatter phase. The influence of the hadronic equation of state on the phase\ntransition and neutron star properties are investigated. We find that a neutron\nstar possesses a large population of hyperons, but it is not dense enough to\npossess a pure quark core. Whether the mixed phase of hadronic and quark matter\nexist in the core of neutron stars depends on the RMF parameters used.", "category": "nucl-th" }, { "text": "Auxiliary Field Quantum Monte Carlo for Nuclear Physics on the Lattice: We employ constrained path Auxiliary Field Quantum Monte Carlo (AFQMC) in the\npursuit of studying physical nuclear systems using a lattice formalism. Since\nAFQMC has been widely used in the study of condensed-matter systems such as the\nHubbard model, we benchmark our method against published results for both one-\nand two-dimensional Hubbard model calculations. We then turn our attention to\ncold-atomic and nuclear systems. We use an onsite contact interaction that can\nbe tuned in order to reproduce the known scattering length and effective range\nof a given interaction. Developing this machinery allows us to extend our\ncalculations to study nuclear systems within a lattice formalism. We perform\ninitial calculations for a range of nuclear systems from two- to few-body\nneutron systems.", "category": "nucl-th" }, { "text": "The Single State Dominance Hypothesis and the Two-Neutrino Double Beta\n Decay of Mo100: The hypothesis of the single state dominance (SSD) in the calculation of the\ntwo-neutrino double beta decay of Mo100 is tested by exact consideration of the\nenergy denominators of the perturbation theory. Both transitions to the ground\nstate as well as to the 0+ and 2+ excited states of the final nucleus Ru100 are\nconsidered. We demonstrate, that by experimental investigation of the single\nelectron energy distribution and the angular correlation of the outgoing\nelectrons, the SSD hypothesis can be confirmed or ruled out by a precise\ntwo-neutrino double beta decay measurement (e.g. by NEMO III collaboration).", "category": "nucl-th" }, { "text": "A novel treatment of the proton-proton Coulomb force in elastic\n proton-deuteron Faddeev calculations: We propose a novel approach to incorporate the proton-proton (pp) Coulomb\nforce into the three-nucleon (3N) Faddeev calculations. The main new ingredient\nis a 3-dimensional screened pp Coulomb t-matrix obtained by a numerical\nsolution of the 3-dimensional Lippmann-Schwinger (LS) equation. We demonstrate\nnumerically and provide analytical insight that the elastic proton-deuteron\n(pd) observables can be determined directly from the resulting on shell 3N\namplitude increasing the screening radius. The screening limit exists without\nthe need of renormalisation not only for observables but for the elastic pd\namplitude itself.", "category": "nucl-th" }, { "text": "Thermalization through Hagedorn states - the importance of multiparticle\n collisions: Quick chemical equilibration times of hadrons within a hadron gas are\nexplained dynamically using Hagedorn states, which drive particles into\nequilibrium close to the critical temperature. Within this scheme master\nequations are employed for the chemical equilibration of various hadronic\nparticles like (strange) baryon and antibaryons. A comparison of the Hagedorn\nmodel to recent lattice results is made and it is found that for both Tc =176\nMeV and Tc=196 MeV, the hadrons can reach chemical equilibrium almost\nimmediately, well before the chemical freeze-out temperatures found in thermal\nfits for a hadron gas without Hagedorn states.", "category": "nucl-th" }, { "text": "Stellar weak-interaction rates for $rp$-process waiting-point nuclei\n from projected shell model: We propose a projected shell model (PSM) for description of stellar\nweak-interaction rates between even-even and odd-odd nuclei with extended\nconfiguration space where up to six-quasiparticle (qp) configurations are\nincluded, and the stellar weak-interaction rates for eight $rp$-process\nwaiting-point (WP) nuclei, $^{64}$Ge, $^{68}$Se, $^{72}$Kr, $^{76}$Sr,\n$^{80}$Zr, $^{84}$Mo, $^{88}$Ru and $^{92}$Pd, are calculated and analyzed for\nthe first time within the model. Higher-order qp configurations are found to\naffect the underlying Gamow-Teller strength distributions and the corresponding\nstellar weak-interaction rates. Under $rp$-process environments with high\ntemperatures and densities, on one hand, thermal population of excited states\nof parent nuclei tends to decrease the stellar $\\beta^+$ decay rates. On the\nother hand, the possibility of electron capture (EC) tends to provide\nincreasing contribution to the rates with temperature and density. The\neffective half-lives of WP nuclei under the $rp$-process peak condition are\npredicted to be reduced as compared with the terrestrial case, especially for\n$^{64}$Ge and $^{68}$Se.", "category": "nucl-th" }, { "text": "Virtual Compton Scattering off the Nucleon in Chiral Perturbation Theory: We investigate the spin-independent part of the virtual Compton scattering\n(VCS) amplitude off the nucleon within the framework of chiral perturbation\ntheory. We perform a consistent calculation to third order in external momenta\naccording to Weinberg's power counting. With this calculation we can determine\nthe second- and fourth-order structure-dependent coefficients of the general\nlow-energy expansion of the spin-averaged VCS amplitude based on gauge\ninvariance, crossing symmetry and the discrete symmetries. We discuss the\nkinematical regime to which our calculation can be applied and compare our\nexpansion with the multipole expansion by Guichon, Liu and Thomas. We establish\nthe connection of our calculation with the generalized polarizabilities of the\nnucleon where it is possible.", "category": "nucl-th" }, { "text": "Compton Scattering on 4He with Nuclear One- and Two-Body Densities: We present the first \\emph{ab initio} calculation of elastic Compton\nscattering from 4He. It is carried out to $\\mathcal{O}(e^2 \\delta^3)$ [N3LO] in\nthe $\\delta$ expansion of $\\chi$EFT. At this order and for this target, the\nonly free parameters are the scalar-isoscalar electric and magnetic dipole\npolarisabilities of the nucleon. Adopting current values for these yields a\nparameter-free prediction. This compares favourably with the world data from\nHI$\\gamma$S, Illinois and Lund for photon energies\n$50\\;\\mathrm{MeV}\\lesssim\\omega\\lesssim120\\;\\mathrm{MeV}$ within our\ntheoretical uncertainties of $\\pm10\\%$. We predict a cross section up to 7\ntimes that for deuterium. As in 3He, this emphasises and tests the key role of\nmeson-exchange currents between np pairs in Compton scattering on light nuclei.\nWe assess the sensitivity of the cross section and beam asymmetry to the\nnucleon polarisabilities, providing clear guidance to future experiments\nseeking to further constrain them. The calculation becomes tractable by use of\nthe Transition Density Method. The one- and two-body densities generated from 5\nchiral potentials and the AV18$+$UIX potential are available using the python\npackage provided at \\url{https://pypi.org/project/nucdens/}.", "category": "nucl-th" }, { "text": "$\u03b1$ Decays in Superstrong Static Electric Fields: Superstrong static electric fields could deform Coulomb barriers between\n$\\alpha$ clusters and daughter nuclei, and bring up the possibility of speeding\nup $\\alpha$ decays. We adopt a simplified model for the spherical $\\alpha$\nemitter $^{212}$Po and study its responses to superstrong static electric\nfields. We find that, superstrong electric fields with field strengths\n$|\\mathbf{E}|\\sim0.1$ MV/fm could turn the angular distribution of $\\alpha$\nemissions from isotropic to strongly anisotropic, and speed up $\\alpha$ decays\nby more than one order of magnitude. We also study the influences of\nsuperstrong electric fields along the Po isotope chains, and discuss the\nimplications of our studies on $\\alpha$ decays in superstrong monochromatic\nlaser fields. The study here might be helpful for future theoretical studies of\n$\\alpha$ decay in realistic superstrong laser fields.", "category": "nucl-th" }, { "text": "Hadron-quark mixed phase in hyperon stars: We analyze the different possibilities for the hadron-quark phase transition\noccurring in beta-stable matter including hyperons in neutron stars. We use a\nBrueckner-Hartree-Fock approach including hyperons for the hadronic equation of\nstate and a generalized MIT bag model for the quark part. We then point out in\ndetail the differences between Maxwell and Gibbs phase transition constructions\nincluding the effects of surface tension and electromagnetic screening. We find\nonly a small influence on the maximum neutron star mass, whereas the radius of\nthe star and in particular its internal structure are more affected.", "category": "nucl-th" }, { "text": "Estimating magnetar radii with an empirical meta-model: The presence of strong magnetic fields in neutron stars, such as in\nmagnetars, may significantly affect their crust-core transition properties and\nthe crust size. This knowledge is crucial in the correct interpretation of\nastrophysical phenomena involving magnetars, such as glitches in observed\nrotation frequencies, cooling, bursts and possibly tidal polarizabilities. A\nrecently developed meta-modelling technique allows exploring the model\ndependence of density functional theory equation of state calculations. In this\nwork, we extend this meta-model to investigate the effect of strong magnetic\nfields on spinodal instabilities of neutron star matter and the associated\ncrust-core properties. Both Tolman-Oppenheimer-Volkov and a full\nself-consistent numerical calculations are performed for the neutron star\nstructure, the results being quantitatively different for strong magnetic\nfields.", "category": "nucl-th" }, { "text": "Transport Coefficient to Trace Anomaly in the Clustering of Color\n Sources Approach: From our previously obtained shear viscosity to entropy density ratio\n($\\eta/s$) in the framework of clustering of color sources (Color String\nPercolation Model: CSPM), we calculate the jet quenching parameter $\\hat {q}$\nand trace anomaly $\\Delta = (\\varepsilon -3\\it p)/T^{4}$ as a function of\ntemperature. It is shown that the scaled $\\hat {q}/T^{3}$ is in agreement with\nthe recent JET Collaboration estimates. The inverse of $\\eta/s$ is found to\nrepresent $\\Delta$. The results for $\\Delta$ are in excellent agreement with\nLattice Quantum Chromo Dynamics (LQCD) simulations. From the trace anomaly and\nenergy density $\\epsilon$, the equation of state is obtained as a function of\ntemperature and compared with LQCD simulations. It is possible that there is a\ndirect connection between the $\\eta/s$ and $\\Delta$. Thus the estimate of\ntransport coefficient $\\eta/s$ provides $\\hat {q}$ and $\\Delta$ as a function\nof temperature. Both $\\Delta$ and $\\eta/s$ describe the transition from a\nstrongly coupled QGP to a weakly coupled QGP.", "category": "nucl-th" }, { "text": "Collisional energy loss and the suppression of high $p_T$ hadrons: We calculate nuclear suppression factor ($R_{AA}$) for light hadrons by\ntaking only the elastic processes and argue that in the measured $p_T$ domain\nof RHIC, collisional rather than the radiative processes is the dominant\nmechanism for partonic energy loss.", "category": "nucl-th" }, { "text": "Constraining URCA cooling of neutron stars from the neutron radius of\n 208Pb: Recent observations by the Chandra observatory suggest that some neutron\nstars may cool rapidly, perhaps by the direct URCA process which requires a\nhigh proton fraction. The proton fraction is determined by the nuclear symmetry\nenergy whose density dependence may be constrained by measuring the neutron\nradius of a heavy nucleus, such as 208Pb. Such a measurement is necessary for a\nreliable extrapolation of the proton fraction to the higher densities present\nin the neutron star. A large neutron radius in 208Pb implies a stiff symmetry\nenergy that grows rapidly with density, thereby favoring a high proton fraction\nand allowing direct URCA cooling. Predictions for the neutron radius in 208Pb\nare correlated to the proton fraction in dense matter by using a variety of\nrelativistic effective field-theory models. Models that predict a neutron (Rn)\nminus proton (Rp) root-mean-square radius in 208Pb to be Rn-Rp<0.20 fm have\nproton fractions too small to allow the direct URCA cooling of 1.4 solar-mass\nneutron stars. Conversely, if Rn-Rp>0.25 fm, the direct URCA process is allowed\n(by all models) to cool down a 1.4 solar-mass neutron star. The Parity Radius\nExperiment at Jefferson Laboratory aims to measure the neutron radius in 208Pb\naccurately and model independently via parity-violating electron scattering.\nSuch a measurement would greatly enhance our ability to either confirm or\ndismiss the direct URCA cooling of neutron stars.", "category": "nucl-th" }, { "text": "Factorization Breaking of $A^T_d$ for polarized deuteron targets in a\n relativistic framework: We discuss the possible factorization of the tensor asymmetry $A^T_d$\nmeasured for polarized deuteron targets within a relativistic framework. We\ndefine a reduced asymmetry and find that factorization holds only in plane wave\nimpulse approximation and if p-waves are neglected. Our numerical results show\na strong factorization breaking once final state interactions are included. We\nalso compare the d-wave content of the wave functions with the size of the\nfactored, reduced asymmetry and find that there is no systematic relationship\nof this quantity to the d-wave probability of the various wave functions.", "category": "nucl-th" }, { "text": "Uncertainty Quantification for Optical Model Parameters: Although uncertainty quantification has been making its way into nuclear\ntheory, these methods have yet to be explored in the context of reaction\ntheory. For example, it is well known that different parameterizations of the\noptical potential can result in different cross sections, but these differences\nhave not been systematically studied and quantified. The purpose of this work\nis to investigate the uncertainties in nuclear reactions that result from\nfitting a given model to elastic-scattering data, as well as to study how these\nuncertainties propagate to the inelastic and transfer channels. We use\nstatistical methods to determine a best fit and create corresponding 95\\%\nconfidence bands. A simple model of the process is fit to elastic-scattering\ndata and used to predict either inelastic or transfer cross sections. In this\ninitial work, we assume that our model is correct, and the only uncertainties\ncome from the variation of the fit parameters. We study a number of reactions\ninvolving neutron and deuteron projectiles with energies in the range of 5-25\nMeV/u, on targets with mass $A$=12-208. We investigate the correlations between\nthe parameters in the fit. The case of deuterons on $^{12}$C is discussed in\ndetail: the elastic-scattering fit and the prediction of $^{12}$C(d,p)$^{13}$C\ntransfer angular distributions, using both uncorrelated and correlated $\\chi^2$\nminimization functions. The general features for all cases are compiled in a\nsystematic manner to identify trends. Our work shows that, in many cases, the\ncorrelated $\\chi ^2$ functions (in comparison to the uncorrelated $\\chi^2$\nfunctions) provide a more natural parameterization of the process. These\ncorrelated functions do, however, produce broader confidence bands. Further\noptimization may require improvement in the models themselves and/or more\ninformation included in the fit.", "category": "nucl-th" }, { "text": "Reduced transition probabilities for the gamma decay of the 7.8 eV\n isomer in $^{229}$Th: The reduced magnetic dipole and electric quadrupole transition probabilities\nfor the radiative decay of the $^{229}$Th 7.8 eV isomer to the ground state are\npredicted within a detailed nuclear-structure model approach. We show that the\npresence and decay of this isomer can only be accounted for by the Coriolis\nmixing emerging from a remarkably fine interplay between the coherent\nquadrupole-octupole motion of the nuclear core and the single-nucleon motion\nwithin a reflection-asymmetric deformed potential. We find that the magnetic\ndipole transition probability which determines the radiative lifetime of the\nisomer is considerably smaller than presently estimated. The so-far disregarded\nelectric quadrupole component may have non-negligible contributions to the\ninternal conversion channel. These findings support new directions in the\nexperimental search of the $^{229}$Th transition frequency for the development\nof a future nuclear frequency standard.", "category": "nucl-th" }, { "text": "Exotic hadrons and hadron-hadron interactions in heavy ion collisions: We discuss the exotic hadron structure and hadron-hadron interactions in view\nof heavy ion collisions. First, we demonstrate that a hadronic molecule with a\nlarge spatial size would be produced more abundantly in the coalescence model\ncompared with the statistical model result. Secondly, we constrain the\nLambda-Lambda interaction by using the recently measured Lambda-Lambda\ncorrelation data. We find that the RHIC-STAR data favor the Lambda-Lambda\nscattering parameters in the range 1/a_0 <= -0.8 fm^{-1} and r_{eff} >= 3 fm.", "category": "nucl-th" }, { "text": "Fusion reactions in plasmas as probe of the high-momentum tail of\n particle distributions: In fusion reactions, the Coulomb barrier selects particles from the\nhigh-momentum part of the distribution. Therefore, small variations of the\nhigh-momentum tail of the velocity distribution can produce strong effects on\nfusion rates. In plasmas several potential mechanisms exist that can produce\ndeviations from the standard Maxwell-Boltzmann distribution. Quantum broadening\nof the energy-momentum dispersion relation of the plasma quasi-particles\nmodifies the high-momentum tail and could explain the fusion-rate enhancement\nobserved in low-energy nuclear reaction experiments.", "category": "nucl-th" }, { "text": "Short-range correlations in semi-exclusive electron scattering\n experiments: One-nucleon emission electron scattering experiments are studied with a model\nthat considers short--range correlations up to the first order in the number of\ncorrelation lines. The proper normalization of the many-body wave functions\nrequires the evaluation of two- and three-point diagrams, the last ones usually\nneglected in the literature. When all these diagrams are included the effects\nof the short-range correlations are rather small. The results of our\ncalculations are compared with experimental data taken on $^{16}$O.", "category": "nucl-th" }, { "text": "Meson-induced pentaquark productions: Production cross sections of the pentaquark Theta+ baryon in the\nmeson-induced reactions are calculated for JP=1/2+- and 3/2+- cases. Through\nthe comparison with the previous measurements at KEK, several quantum numbers\nare excluded. The remaining possibilities can be used to cast the upper limit\non the Theta+ width, combining with the result from the J-PARC E19 experiment.", "category": "nucl-th" }, { "text": "The Impact of Anisotropy on Neutron Star Properties: Insights from I-f-C\n Universal Relations: This study presents a universal relation for anisotropic neutron stars,\ncalled the $I-f-C$ relation, which accounts for the local anisotropic pressure\nusing the Quasi-Local (QL) Model proposed by Horvat et al. \\cite{QL_Model} to\ndescribe the anisotropy inside the neutron star. This study analyzes\napproximately 60 unified tabulated EoS-ensembles, spanning from relativistic to\nnon-relativistic mean-field models, that comply with multimessenger constraints\nand cover a broad range of stiffness. The results indicate that the\nrelationship between the parameters becomes more robust with positive\nanisotropy, while it weakens with negative anisotropy. With the help of the\nGW170817 \\& GW190814 tidal deformability limit, a theoretical limit for the\ncanonical $f$-mode frequency for both isotropic and anisotropic stars is\nestablished. For isotropic case the canonical $f$-mode frequency for event\nGW170817 \\& GW190814 is $f_{1.4} = 2.605^{+0.487} _ {-0.459}\\ \\mathrm{kHz}$ and\n$ f_{1.4} = 2.093^{+0.150} _ {-0.125} \\ \\mathrm{kHz}$ respectively. These\nestablished relationships have the potential to serve as a reliable tool to\nlimit the equation of state of nuclear matter when measurements of relevant\nobservables are obtained.", "category": "nucl-th" }, { "text": "The freeze-out mechanism and phase-space density in ultrarelativistic\n heavy-ion collisions: We explore the consequences of a freeze-out criterion for heavy-ion\ncollisions, based on pion escape probabilities from the hot and dense but\nrapidly expanding collision region. The influence of the expansion and the\nscattering rate on the escape probability is studied. The temperature\ndependence of this scattering rate favors a low freeze-out temperature of ~100\nMeV. In general, our results support freeze-out along finite four-volumes\nrather than sharp three-dimensional hypersurfaces, with high-pt particles\ndecoupling earlier from smaller volumes. We compare our approach to the\nproposed universal freeze-out criteria using the pion phase-space density and\nits mean free path.", "category": "nucl-th" }, { "text": "Isospin splitting of pion elliptic flow in relativistic heavy-ion\n collisions: Based on the framework of an extended multiphase transport model with\nmean-field potentials in both the partonic phase and the hadronic phase, we\nexplain the elliptic flow difference between $\\pi^+$ and $\\pi^-$ in the\nbeam-energy scan program at the relativistic heavy-ion collider by\nincorporating the vector-isovector potential for quarks and antiquarks with\ndifferent isospins. It is found that the isospin splitting of pion elliptic\nflow favors a strong vector-isovector interaction, and thus serves as a probe\nof the quark matter equation of state as well as the QCD phase structure at\nfinite baryon and isospin chemical potentials.", "category": "nucl-th" }, { "text": "Efimov resonances above four-boson threshold: Four-boson Efimov physics is well known in the negative energy regime but far\nless above the four-body breakup threshold. The part of this region with\nnegative two-boson scattering length is studied solving rigorous four-particle\nscattering equations for transition operators in the momentum space. Moving\naway from the unitary limit the Efimov tetramers evolve from unstable bound\nstates into resonances. Their energies and widths are studied as functions of\nthe two-boson scattering length; a universal behavior is established and given\nin a dimensionless representation. The Efimov tetramers have finite width in\nthe whole regime; they broaden rapidly in the resonance regime but remain\nnarrower than the associated trimer. The resonant behavior is most clearly seen\nin the four-particle recombination rate.", "category": "nucl-th" }, { "text": "Do deviations of neutron scattering widths distribution from the\n Porter-Thomas law indicate on failure of the Random Matrix theory?: Deviations of neutron scattering width distributions from the Porter-Thomas\nlaw due to resonances overlapping are calculated in the extended framework of\nthe random matrix approach.", "category": "nucl-th" }, { "text": "Kaon Energies in Dense Matter: We discuss the role of kaon-nucleon and nucleon-nucleon correlations in kaon\ncondensation in dense matter. Correlations raise the threshold density for kaon\ncondensation, possibly to densities higher than those encountered in stable\nneutron stars.", "category": "nucl-th" }, { "text": "On the thermalization of quarkonia at the LHC: We argue that the relative yields of $\\Upsilon$ states observed at the LHC\ncan be understood as bottomonium states coming to early thermal equilibrium and\nthen freezing out. The bottomonium freezeout temperature is approximately 250\nMeV. We examine its systematics as a function of centrality. We remark on the\ninteresting differences seen by the CMS and ALICE experiments in the charmonium\nsector.", "category": "nucl-th" }, { "text": "Strange Goings on in Quark Matter: We review recent work on how the superfluid state of three flavor quark\nmatter is affected by non-zero quark masses and chemical potentials.", "category": "nucl-th" }, { "text": "Effective field theory approaches to pion production in proton-proton\n collisions: I critically review the status of computations of threshold pion production\nin proton-proton collisions in the framework of effective field theory\napproaches or variants thereof. I also present the results of a novel\ndiagrammatic scheme.", "category": "nucl-th" }, { "text": "Cross sections for Coulomb and nuclear breakup of three-body halo nuclei: All possible dissociation cross sections for the loosely bound three-body\nhalo nuclei $^6$He (n+n+$\\alpha$) and $^{11}$Li (n+n+$^{9}$Li) are computed as\nfunctions of target and beam energy. Both Coulomb and nuclear interactions are\nincluded in the same theoretical framework. The measurements agree with the\ncalculations for energies above 100 Mev/nucleon. The largest cross sections\ncorrespond to final states with zero or three particles for heavy and with two\nneutrons for light targets.", "category": "nucl-th" }, { "text": "Clusterization and deformation of multi-$\u039b$ hypernuclei within\n relativistic mean-field model: Deformed multi-$\\Lambda$ hypernuclei are studied within a relativistic\nmean-field model. In this paper, we take some $N=Z$ \"hyper isotope\" chains,\ni.e., $^{8+n}_{\\ \\ n\\Lambda}{\\rm Be}$, $^{20+n}_{\\ \\ \\ n\\Lambda}{\\rm Ne}$, and\n$^{28+n}_{\\ \\ \\ n\\Lambda}{\\rm Si}$ systems where $n = 2$, $4$ for Be, and $n =\n2$, $8$ for Ne and Si. A sign of two-$^6_{2\\Lambda}$He cluster structure is\nobserved in the two-body correlation in $^{12}_{4\\Lambda}$Be. In the Ne hyper\nisotopes, the deformation is slightly reduced by addition of $\\Lambda$ hyperons\nwhereas it is significantly reduced or even disappears in the Si hyper\nisotopes.", "category": "nucl-th" }, { "text": "Observable consequences of event-by-event fluctuations of HBT radii: We explore the effects of event-by-event fluctuations of Hanbury Brown-Twiss\n(HBT) radii and show how they can be observed experimentally. The relation of\nmeasured HBT radii extracted from ensemble-averaged correlation functions to\nthe mean of their event-by-event probability distribution is clarified. We\npropose a method to experimentally determine the mean and variance of this\ndistribution and test it on an ensemble of fluctuating events generated with\nthe viscous hydrodynamic code VISH2+1. Using the same code, the sensitivity of\nthe mean and variance of the HBT radii to the specific QGP shear viscosity\n$\\eta/s$ is studied. We report sensitivity of the mean pion HBT radii and their\nvariances to the temperature dependence of $\\eta/s$ near the quark-hadron\ntransition at a level similar (10-20%) to that which was previously observed\nfor elliptic and quadrangular flow of charged hadrons [1].", "category": "nucl-th" }, { "text": "Strangeness Balance in HADES Experiments and the Xi- Enhancement: HADES data on a strangeness production in Ar+KCl collisions at 1.76A GeV are\nanalyzed within a minimal statistical model. The total negative strangeness\ncontent is fixed by the observed K^+ multiplicities on event-by-event basis.\nParticles with negative strangeness are assumed to remain in chemical\nequilibrium with themselves and in thermal equilibrium with the environment\nuntil a common freeze-out. Exact strangeness conservation in each collision\nevent is explicitly preserved. This implies that Xi baryons can be released\nonly in events where two or more kaons are produced. An increase of the\nfireball volume due to application of a centrality trigger in HADES experiments\nis taken into account. We find that experimental ratios of K-/K+, Lambda/K+ and\nSigma/K+ can be satisfactorily described provided in-medium potentials are\ntaken into account. However, the calculated Xi-/Lambda/K+ ratio proves to be\nsignificantly smaller compared to the measured value (8 times lower than the\nexperimental median value and 3 times lower than the lower error bar). Various\nscenarios to explain observed Xi enhancement are discussed. Arguments are given\nin favor of the Xi production in direct reactions. The rates of the possible\nproduction processes are estimated and compared.", "category": "nucl-th" }, { "text": "Cluster and hyper-cluster production in relativistic heavy-ion\n collisions within the Parton-Hadron-Quantum-Molecular-Dynamics approach: We study cluster and hypernuclei production in heavy-ion collisions at\nrelativistic energies employing the Parton-Hadron-Quantum-Molecular-Dynamics\n(PHQMD) approach, a microscopic n-body transport model based on the QMD\npropagation of the baryonic degrees of freedom with density dependent 2-body\npotential interactions. All other ingredients of PHQMD, including the collision\nintegral and the treatment of the quark-gluon plasma (QGP) phase, are adopted\nfrom the Parton-Hadron-String Dynamics (PHSD) approach. In PHQMD the cluster\nformation occurs dynamically, caused by the interactions. The clusters are\nrecognized by the Minimum Spanning Tree (MST) algorithm. We present the PHQMD\nresults for cluster and hypernuclei formation in comparison with the available\nexperimental data at AGS, SPS, RHIC-BES and RHIC fixed target energies. We also\nprovide predictions on cluster production for the upcoming FAIR and NICA\nexperiments. PHQMD allows to study the time evolution of formed clusters and\nthe origin of their production, which helps to understand how such weakly bound\nobjects are formed and survive in the rather dense and hot environment created\nin heavy-ion collisions. It offers therefore an explanation of the 'ice in the\nfire' puzzle.", "category": "nucl-th" }, { "text": "Spinodal decomposition of low-density asymmetric nuclear matter: We investigate the dynamical properties of asymmetric nuclear matter at low\ndensity. The occurrence of new instabilities, that lead the system to a\ndynamical fragment formation, is illustrated, discussing in particular the\ncharge symmetry dependence of the structure of the most important unstable\nmodes. We observe that instabilities are reduced by charge asymmetry, leading\nto larger size and time scales in the fragmentation process. Configurations\nwith less asymmetric fragments surrounded by a more asymmetric gas are\nfavoured. Interesting variances with respect to a pure thermodynamical\nprediction are revealed, that can be checked experimentally. All these features\nare deeply related to the structure of the symmetry term in the nuclear\nEquation of State (EOS) and could be used to extract information on the low\ndensity part of the EOS.", "category": "nucl-th" }, { "text": "Study of np-scattering for S, P and D Waves using Deng-Fan Potential by\n Phase Function Method: In this paper, the np - scattering phase shifts and cross section for S,P and\nD partial waves have been obtained for energies below the pion threshold, by\nconsidering Deng-Fan potential as model of interaction. The radial time\nindependent Schr\\\"odinger equation has been analytically solved using Nikiforov\n- Uvarov method to obtain the energy expression for ground state of np system.\nUtilising this, the scattering phase shifts for $^3S_1$ have been obtained\nusing phase function method. The phase equations for various scattering states\n$^1S_0$, $^1P_1$, $^3P_{0,1,2}$, $^1D_2$, and $^3D_{1,2,3}$ have been\nnumerically solved for obtaining corresponding scattering phase shifts and\ntheir respective partial cross section. The total scattering cross sections\ncomputed at various energies are found to be closely matching with experimental\ndata. The low energy scattering parameters determined from scattering phase\nshifts of $^3S_1$ and $^1S_0$ are reasonably close to experimental ones. Hence,\nDeng-Fan potential is a good phenomenological potential to understand the np -\nscattering system.", "category": "nucl-th" }, { "text": "A microscopic benchmark-study of triaxiality in low-lying states of 76Kr: We report on a seven-dimensional generator coordinate calculation in the two\ndeformation parameters $\\beta$ and $\\gamma$ together with projection on\nthree-dimensional angular momentum and two particle numbers for the low-lying\nstates in $^{76}$Kr. These calculations are based on covariant density\nfunctional theory. Excellent agreement is found with the data for the spectrum\nand the electric multipole transition strengths. This answers the important\nquestion of dynamic correlations and triaxiality in a fully microscopic way. We\nfind that triaxial configurations dominate both the ground state and the quasi\n$\\gamma$-band. This yields a different picture from the simple interpretation\nin terms of \"coexistence of a prolate ground state with an oblate low-lying\nexcited state\", which is based on the measured sign of spectroscopic quadrupole\nmoments. This study also provides for the first time a benchmark for the\ncollective Hamiltonian in five dimensions. Moreover, we point out that the\nstaggering phase of the $\\gamma$-band is not a safe signature for rigid\ntriaxiality of the low-energy structure.", "category": "nucl-th" }, { "text": "Foundations of the proxy-SU(3) symmetry in heavy nuclei: We show that within the proxy-SU(3) scheme the wave functions of the normal\nparity orbitals in a given nuclear shell are affected very little as a result\nof the replacement of the abnormal parity orbitals by their 0[110] proxy-SU(3)\ncounterparts.", "category": "nucl-th" }, { "text": "Kaon fragmentation function from NJL-jet model: The NJL-jet model provides a sound framework for calculating the\nfragmentation func- tions in an effective chiral quark theory, where the\nmomentum and isospin sum rules are satisfied without the introduction of ad hoc\nparameters [1]. Earlier studies of the pion fragmentation func- tions using the\nNambu-Jona-Lasinio (NJL) model within this framework showed good qualitative\nagreement with the empirical parameterizations. Here we extend the NJL-jet\nmodel by including the strange quark. The corrections to the pion fragmentation\nfunction and corresponding kaon fragmen- tation functions are calculated using\nthe elementary quark to quark-meson fragmentation functions from NJL. The\nresults for the kaon fragmentation function exhibit a qualitative agreement\nwith the empirical parameterizations, while the unfavored strange quark\nfragmentation to pions is shown to be of the same order of magnitude as the\nunfavored light quark's. The results of these studies are expected to provide\nimportant guidance for the analysis of a large variety of semi-inclusive data.", "category": "nucl-th" }, { "text": "From QCD Symmetries to Nuclei and Neutron Stars: Global symmetries and symmetry breaking patterns of QCD with light quarks, in\nparticular chiral symmetry, provide basic guidance not only for low-energy\nhadron physics but also for nuclear forces and the nuclear many-body problem.\nRecent developments of Chiral Effective Field Theory applications to nuclear\nand neutron matter are summarized, with special emphasis on a\n(non-perturbative) extension using functional renormalisation group methods.\nTopics include: nuclear thermodynamics, extrapolations to dense baryonic matter\nand constraints from neutron star observables.", "category": "nucl-th" }, { "text": "Extended parity doublet model with a new transport code: A new transport code \"DaeJeon Boltzmann-Uehling-Uhlenbeck (DJBUU)\" had been\ndeveloped and enables to describe the dynamics of heavy-ion collisions in\nlow-energy region. To confirm the validity of the new code, we first calculate\nAu + Au collisions at Ebeam = 100 and 400A MeV and also perform the box\ncalculation to check the detail of collisions and Pauli blocking without\nmean-field potential as suggested by the Transport Code Comparison Project.\nAfter confirming the validity of new transport code, we study low-energy\nheavy-ion collisions with an extended parity doublet model. Since the\ndistinctive feature of the parity doublet model is the existence of the chiral\ninvariant mass that contributes to the nucleon mass, we investigate how\nphysical quantities depend on the chiral invariant mass in heavy ion collisions\nat low energies. For this, we calculate physical quantities such as the\neffective nucleon mass in central collisions and transverse flow in\nsemi-central collisions of Au + Au at Ebeam = 400A MeV with different values of\nthe chiral invariant masses.", "category": "nucl-th" }, { "text": "The adjoint neutron transport equation and the statistical approach for\n its solution: The adjoint equation was introduced in the early days of neutron transport\nand its solution, the neutron importance, has ben used for several applications\nin neutronics. The work presents at first a critical review of the adjoint\nneutron transport equation. Afterwards, the adjont model is constructed for a\nreference physical situation, for which an analytical approach is viable, i.e.\nan infinite homogeneous scattering medium. This problem leads to an equation\nthat is the adjoint of the slowing-down equation that is well-known in nuclear\nreactor physics. A general closed-form analytical solution to such adjoint\nequation is obtained by a procedure that can be used also to derive the\nclassical Placzek functions. This solution constitutes a benchmark for any\nstatistical or numerical approach to the adjoint equation. A sampling technique\nto evaluate the adjoint flux for the transport equation is then proposed and\nphysically interpreted as a transport model for pseudo-particles. This can be\ndone by introducing appropriate kernels describing the transfer of the\npseudo-particles in phase space. This technique allows estimating the\nimportance function by a standard Monte Carlo approach. The sampling scheme is\nvalidated by comparison with the analytical results previously obtained.", "category": "nucl-th" }, { "text": "The stifness of the supranuclear equation of state (once again): We revisit the present status of the stiffness of the supranuclear equations\nof state, particularly the solutions that increase the stiffness in the\npresence of hyperons, the putative transition to a quark matter phase and the\nrobustness of massive compact star observations.", "category": "nucl-th" }, { "text": "Spin 1 inversion: a Majorana tensor force for deuteron alpha scattering: We demonstrate, for the first time, successful S-matrix to potential\ninversion for spin one projectiles with non-diagonal $S^j_{ll'}$ yielding a\n$T_{\\rm R}$ interaction. The method is a generalization of the\niterative-perturbative, IP, method. We present a test case indicating the\ndegree of uniqueness of the potential. The method is adapted, using established\nprocedures, into direct observable to potential inversion, fitting $\\sigma$,\n${\\rm i}T_{11}$, $T_{20}$, $T_{21}$ and $T_{22}$ for d + alpha scattering over\na range of energies near 10 MeV. The $T_{\\rm R}$ interaction which we find is\nvery different from that proposed elsewhere, both real and imaginary parts\nbeing very different for odd and even parity channels.", "category": "nucl-th" }, { "text": "The pp -> p Lambda K+ and pp -> p Sigma0 K+ Reactions in the Chiral\n Unitary Approach: We study the pp -> p Lambda K+ and pp -> p Sigma0 K+ reactions near threshold\nby using a chiral unitary approach. We consider the single-pion and single-kaon\nexchange as well as the final state interactions of nucleon-hyperon, K-hyperon\nand K-nucleon systems. Our results on the total cross section of the pp -> p\nLambda K+ reaction is consistent with the experimental data, and the\nexperimental observed strong suppression of Sigma0 production compared to\nLambda production at the same excess energy can also be explained in our model.", "category": "nucl-th" }, { "text": "Electric-dipole transitions in $^6$Li with a fully microscopic six-body\n calculation: Exploring new excitation modes and the role of the nuclear clustering has\nbeen of great interest. An interesting speculation was made in the recent\nphotoabsorption measurement of $^6$Li that implied the importance of the\nnuclear clustering. To understand the excitation mechanism of $^6$Li, we\nperform a fully microscopic six-body calculation on the electric-dipole ($E1$)\ntransitions and discuss how $^6$Li is excited by the $E1$ field as a function\nof the excitation energy. We show the various cluster components in the\nsix-body wave functions and discuss the role of the nuclear clustering in the\n$E1$ excitations of $^6$Li.", "category": "nucl-th" }, { "text": "Pairing correlation involving the continuum states: The Hartree-Fock-Bogoliubov equation for the ground states of even-even\natomic nuclei is solved using the canonical representation in the coordinate\nspace for zero range interactions like the Skyrme force. The gradient method is\nimproved for faster convergence to the solutions under constraint of\northogonality between canonical orbitals. Necessity of the cut-off of the\npairing interaction is shown even when the number of the canonical orbitals are\nrestricted. A repulsive dependence of the interaction on the pairing density is\nintroduced as an implementation of the cut-off which leaves the HFB super\nmatrix state-independent.", "category": "nucl-th" }, { "text": "Neutrino-nucleon scattering rate in proto neutron star matter: We present a calculation of the neutrino-nucleon scattering cross section\nwhich takes into account the nuclear correlations in the relativistic random\nphase approximation. Our approach is based on a quantum hadrodynamics model\nwith exchange of $\\sigma$, $\\omega$, $\\pi$, $\\rho$ and $\\delta$ mesons. In view\nof applications to neutrino transport in the final stages of supernova\nexplosion and protoneutron star cooling, we study the evolution of the neutrino\nmean free path as a function of density, proton-neutron asymmetry and\ntemperature. Special attention was paid to the issues of renormalization of the\nDirac sea, residual interactions in the tensor channel and meson mixing. It is\nfound that RPA corrections, with respect to the mean field approximation,\namount to only 10% to 15% at high density.", "category": "nucl-th" }, { "text": "Nuclear shell structures in terms of classical periodic orbits: Semiclassical periodic-orbit theory (POT) is applied to the physics of\nnuclear structures, with the use of a realistic nuclear mean-field model given\nby the radial power-law potential. Evolution of deformed shell structures,\nwhich are responsible for various nuclear deformations, are clearly understood\nfrom the contribution of short classical periodic orbits (POs). Bifurcations of\nshort POs, which imply underlying local dynamical symmetry, play significant\nrole there. The effect of the spin degree of freedom is also investigated in\nrelevance to the pseudospin symmetry in spherical nuclei and the prolate-oblate\nasymmetry in shell structures of nuclei with quadrupole-type deformations.", "category": "nucl-th" }, { "text": "Photodisintegration of the Three-Nucleon Systems and their\n Polarizabilities: The total photodisintegration cross sections of three-body nuclei are\ncalculated with semirealistic NN potentials below pion threshold. Full final\nstate interaction with Coulomb force is taken into account via the Lorentz\nintegral transform method. The experimental total cross sections are well\ndescribed and the sum rule $\\sigma_{-1}(^3$H) agrees with elastic electron\nscattering data. The calculated ^3He polarizability is 0.15 fm^3.", "category": "nucl-th" }, { "text": "Final state interaction in the pn and nn decay channels of\n $^4_\u039b$He: We study the effects of final state interactions in the non-mesonic weak\ndecay $\\Lambda N \\rightarrow nN$ (n is a neutron and N is either a neutron or a\nproton) of the hypernucleus $_\\Lambda^4$He. Using a three-body model the\neffects of distortion of the interaction of the emitted nucleon pair with the\nresidual nucleus is considered. We also study the influence of the final state\ninteraction between the emitted nucleons using the Migdal-Watson model. The\neffect of spin symmetries in the final state of the pair is also considered.\nBased on our calculations, we conclude that final state interactions play a\nminor role in the kinetic energy spectrum of the emitted nucleon pair.", "category": "nucl-th" }, { "text": "Charmonium dissociation in collision with phi meson in hadronic matter: The phi-charmonium dissociation reactions in hadronic matter are studied.\nUnpolarised cross sections for 12 reactions are calculated in the Born\napproximation, in the quark-interchange mechanism and with a\ntemperature-dependent quark potential. The potential leads to remarkable\ntemperature dependence of the cross sections. With the cross sections and the\nphi distribution function we calculate the dissociation rates of the charmonia\nin the interactions with the phi meson in hadronic matter. The dependence of\nthe rates on temperature and charmonium momentum is meaningful to the influence\nof phi mesons on charmonium suppression.", "category": "nucl-th" }, { "text": "An Extended Approximation for the Lowest-lying States in Odd-mass Nuclei: An enhanced model, based on the Extended Boson Approximation, for the\nlowest-lying states in odd-mass nuclei is presented. Our approach is built on\nthe Quasiparticle Phonon Model, extending it to take into account the ground\nstate correlations due to the action of the Pauli principle more accurately\nthan in the conventional theory. The derived interaction strengths between the\nquasiparticles and the phonons in this model depend on the quasiparticle\noccupation numbers explicitly coupling the odd-mass nucleus equations with\nthose of the even-even core. Within this model we calculated the transition\nprobabilities in several Te, Xe and Ba isotopes with A$\\approx$130.", "category": "nucl-th" }, { "text": "Nuclear Masses and Neutron Stars: Precision mass spectrometry of neutron-rich nuclei is of great relevance for\nastrophysics. Masses of exotic nuclides impose constraints on models for the\nnuclear interaction and thus affect the description of the equation of state of\nnuclear matter, which can be extended to describe neutron-star matter. With\nknowledge of the masses of nuclides near shell closures, one can also derive\nthe neutron-star crustal composition. The Penning-trap mass spectrometer\nISOLTRAP at CERN-ISOLDE has recently achieved a breakthrough measuring the mass\nof 82Zn, which allowed constraining neutron-star crust composition to deeper\nlayers (Wolf et al., PRL 110, 2013). We perform a more detailed study on the\nsequence of nuclei in the outer crust of neutron stars with input from\ndifferent nuclear models to illustrate the sensitivity to masses and the\nrobustness of neutron-star models. The dominant role of the N=50 and N=82\nclosed neutron shells for the crustal composition is confirmed.", "category": "nucl-th" }, { "text": "The method of multiple internal reflections in a description of\n tunneling evolution of nonrelativistic particles and photons: A non-stationary method for tunneling description of non-relativistic\nparticles and photons through a barrier on the basis of consideration of the\nmultiple internal reflections of vawe packets in relation of barrier boundaries\nis presented. The method is described in details and proved in the case of the\none-dimentional tunneling of the particle through the rectangular barrier. For\nproblems of the tunneling of the particle through the spherically symmetric\nbarrier and of the photon through the one-dimensional barrier the amplitudes of\ntransmitted and reflected wave packets in relation to the barrier, times of the\ntunneling and the reflection are found using of the method. Hartman's and\nFletcher's effect is analysed.", "category": "nucl-th" }, { "text": "Relativistic descriptions of inclusive quasielastic electron scattering:\n application to scaling and superscaling ideas: An analysis of inclusive quasielastic electron scattering is presented using\ndifferent descriptions of the final state interactions within the framework of\nthe relativistic impulse approximation. The relativistic Green's function\napproach is compared with calculations based on the use of relativistic purely\nreal mean field potentials in the final state. Both approaches lead to a\nredistribution of the strength but conserving the total flux. Results for the\ndifferential cross section at different energies are presented. Scaling\nproperties are also analyzed and discussed.", "category": "nucl-th" }, { "text": "An effective formulation on quantum hadrodynamics at finite temperatures\n and densities: According to Wick's theorem, the second order self-energy corrections of\nhadrons in the hot and dense nuclear matter are calculated. Furthermore, the\nFeynman rules are summarized, and an effective formulation on quantum\nhadrodynamics at finite temperatures and densities is evaluated. As the strong\ncouplings between nucleons are considered, the self-consistency of this method\nis discussed in the framework of relativistic mean-field approximation. Debye\nscreening masses of the scalar and vector mesons in the hot and dense nuclear\nmatter are calculated with this method in the relativistic mean-field\napproximation. The results are different from those of thermofield dynamics and\nBrown-Rho conjecture. Moreover, the effective masses of the photon and the\nnucleon in the hot and dense nuclear matter are discussed.", "category": "nucl-th" }, { "text": "Gluon distributions in nuclei probed at the CERN Large Hadron Collider: Using updated gluon distributions from global fits to data, we investigate\nthe sensitivity of direct photoproduction of heavy quarks and exclusive\nproduction of vector mesons to varying strength of gluon modifications.\nImplications of using these processes for constraining nuclear gluon\ndistributions are discussed.", "category": "nucl-th" }, { "text": "Isoscalar giant monopole resonance in Sn isotopes using a quantum\n molecular dynamics model: The isoscalar giant monopole resonance (ISGMR) in Sn isotopes and other\nnuclei is investigated in the framework of the isospin-dependent quantum\nmolecular dynamics (IQMD) model. The spectrum of GMR is calculated by taking\nthe root-mean-square (RMS) radius of a nucleus as its monopole moment. The peak\nenergy, the full width at half maximum (FWHM), and the strength of GMR\nextracted by a Gaussian fit to the spectrum have been studied. The GMR peak\nenergies for Sn isotopes from the calculations using a mass-number dependent\nGaussian wave-packet width $\\sigma_r$ for nucleons are found to be\noverestimated and show a weak dependence on the mass number compared with the\nexperimental data. However, it is found that experimental data of the GMR peak\nenergies for $^{56}$Ni, $^{90}$Zr, and $^{208}$Pb as well as Sn isotopes can be\nnicely reproduced after taking into account the isospin dependence in isotope\nchains in addition to the mass number dependence of $\\sigma_r$ for nucleons in\nthe IQMD model calculation.", "category": "nucl-th" }, { "text": "Ferromagnetism of Nuclear Matter in the Relativistic Approach: We study the spin-polarization mechanism in the highly dense nuclear matter\nwith the relativistic mean-field approach. In the relativistic Hartree-Fock\nframework we find that there are two kinds of spin-spin interaction channels,\nwhich are the axial-vector and tensor exchange ones. If each interaction is\nstrong and different sign, the system loses the spherical symmetry and holds\nthe spin-polarization in the high-density region. When the axial-vector\ninteraction is negative enough, the system holds ferromagnetism.", "category": "nucl-th" }, { "text": "Neutron Stars and the High Density Equation of State: One of the key ingredients to understand the properties of neutrons stars is\nthe equation of state at finite densities far beyond nuclear saturation.\nInvestigating the phase structure of quark matter that might be realized in the\ncore of NS inspires theory and observation. We discuss recent results of our\nwork to point out our view on challenges and possibilities in this evolving\nfield by means of a few examples.", "category": "nucl-th" }, { "text": "Embedding nuclear physics inside the unitary window: The large values of the singlet and triplet scattering lengths locate the\ntwo-nucleon system close to the unitary limit, the limit in which these two\nvalues diverge. As a consequence, the system shows a continuous scale\ninvariance which strongly constrains the values of the observables, a\nwell-known fact already noticed a long time ago. The three-nucleon system shows\na discrete scale invariance that can be observed by correlations of the triton\nbinding energy with other observables as the doublet nucleon-deuteron\nscattering length or the alpha-particle binding energy. The low-energy dynamics\nof these systems is universal; it does not depend on the details of the\nparticular way in which the nucleons interact. Instead, it depends on a few\ncontrol parameters, the large values of the scattering lengths and the triton\nbinding energy. Using a potential model with variable strength set to give\nvalues to the control parameters, we study the spectrum of $A=2,3,4,6$ nuclei\nin the region between the unitary limit and their physical values. In\nparticular, we analyze how the binding energies emerge from the unitary limit\nforming the observed levels.", "category": "nucl-th" }, { "text": "Beyond-mean-field theories with zero-range effective interactions. A way\n to handle the ultraviolet divergence: Zero-range effective interactions are commonly used in nuclear physics and in\nother domains to describe many-body systems within the mean-field model. If\nthey are used within a beyond-mean-field framework, contributions to the total\nenergy that display an ultraviolet divergence are found. We propose a general\nstrategy to regularize this divergence and we illustrate it in the case of the\nsecond-order corrections to the equation of state (EOF) of uniform symmetric\nmatter. By setting a momentum cutoff $\\Lambda$, we show that for every\n(physically meaningful) value of $\\Lambda$ it is possible to determine a new\ninteraction such that the EOS with the second-order corrections reproduces the\nempirical EOS, with a fit of the same quality as that obtained at the\nmean-field level.", "category": "nucl-th" }, { "text": "Microsopic nuclear level densities by the shell model Monte Carlo method: The configuration-interaction shell model approach provides an attractive\nframework for the calculation of nuclear level densities in the presence of\ncorrelations, but the large dimensionality of the model space has hindered its\napplication in mid-mass and heavy nuclei. The shell model Monte Carlo (SMMC)\nmethod permits calculations in model spaces that are many orders of magnitude\nlarger than spaces that can be treated by conventional diagonalization methods.\nWe discuss recent progress in the SMMC approach to level densities, and in\nparticular the calculation of level densities in heavy nuclei. We calculate the\ndistribution of the axial quadrupole operator in the laboratory frame at finite\ntemperature and demonstrate that it is a model-independent signature of\ndeformation in the rotational invariant framework of the shell model. We\npropose a method to use these distributions for calculating level densities as\na function of intrinsic deformation.", "category": "nucl-th" }, { "text": "On the Delta-Nucleon and Rho - Pi Splittings: A QCD-inspired Look in\n Free Hadrons versus Nuclei: Relationships between mass intervals for free hadrons and in nuclei are\nstudied in two theoretical approaches inspired by QCD: naive quark model and\nskyrmion model, taking one example each from mesons and baryons, that of pi-rho\nsplitting in mesons, and nucleon-Delta splitting in baryons. Possible\ndeconfinement effects in nuclei are examined.", "category": "nucl-th" }, { "text": "Soft Modes, Quantum Transport and Kinetic Entropy: The effects of the propagation of particles which have a finite life-time and\nan according width in their mass spectrum are discussed in the context of\ntransport descriptions. In the first part the coupling of soft photon modes to\na source of charged particles is studied in a classical model which can be\nsolved completely in analytical terms. The solution corresponds to a\nre-summation of certain field theory diagrams. The general properties of broad\nresonances in dense finite temperature systems are discussed at the example of\nthe $\\rho$-meson in hadronic matter. The second part addresses the problem of\ntransport descriptions which also account for the damping width of the\nparticles. The Kadanoff--Baym equation after gradient approximation together\nwith the $\\Phi$-derivable method of Baym provides a self-consistent and\nconserving scheme. Memory effects appearing in collision term diagrams of\nhigher order are discussed. We derive a generalized expression for the\nnonequilibrium kinetic entropy flow, which includes corrections from\nfluctuations and mass-width effects. In special cases an $H$-theorem is proved.\nMemory effects in collision terms provide contributions to the kinetic entropy\nflow that in the Fermi-liquid case recover the famous bosonic type $T^3 \\ln T$\ncorrection to the specific heat of liquid Helium-3.", "category": "nucl-th" }, { "text": "Nuclear annihilation by antinucleons: We examine the momentum dependence of $\\bar p$$p$ and $\\bar n$$p$\nannihilation cross sections by considering the transmission through a nuclear\npotential and the $\\bar p p$ Coulomb interaction. Compared to the $\\bar n p$\nannihilation cross section, the $\\bar p p$ annihilation cross section is\nsignificantly enhanced by the Coulomb interaction for projectile momenta below\n$p_{\\rm lab} <$ 500 MeV/$c$, and the two annihilation cross sections approach\nthe Pomeranchuk's equality limit [JETP Lett. {\\bb 30}, 423 (1956)] at $p_{\\rm\nlab}\\sim 500$ MeV/$c$. Using these elementary cross sections as the basic input\ndata, the extended Glauber model is employed to evaluate the annihilation cross\nsections for $\\bar n$ and $\\bar p$ interaction with nuclei and the results\ncompare well with experimental data.", "category": "nucl-th" }, { "text": "Explaining Angular Correlations Observed at RHIC with Flow and Local\n Charge Conservation: The observation of fluctuations of parity-odd angular observables at RHIC has\nbeen interpreted as a signal of a local parity violation. We show how the\nobserved signal can be explained by local charge conservation at freeze-out\ncombined with elliptic flow. Calculations from a blast wave model, which\noverlays thermal emission onto a collective flow profile, are shown to account\nfor the experimentally observed signal.", "category": "nucl-th" }, { "text": "Far-from-equilibrium slow modes and momentum anisotropy in expanding\n plasma: The momentum distribution of particle production in heavy-ion collisions\nencodes information about thermalization processes in the early-stage\nquark-gluon plasma. We use kinetic theory to study the far-from-equilibrium\nevolution of an expanding plasma with an anisotropic momentum-space\ndistribution. We identify slow and fast degrees of freedom in the\nfar-from-equilibrium plasma from the evolution of moments of this distribution.\nAt late times, the slow modes correspond to hydrodynamic degrees of freedom and\nare naturally gapped from the fast modes by the inverse of the relaxation time,\n$\\tau_R^{-1}$. At early times, however, there are an infinite number of slow\nmodes with a gap inversely proportional to time, $\\tau^{-1}$. From the\nevolution of the slow modes we generalize the paradigm of the\nfar-from-equilibrium attractor to vector and tensor components of the\nenergy-momentum tensor, and even to higher moments of the distribution function\nthat are not part of the hydrodynamic evolution. We predict that initial-state\nmomentum anisotropy decays slowly in the far-from-equilibrium phase and may\npersist until the relaxation time.", "category": "nucl-th" }, { "text": "Tin-accompanied and true ternary fission of $^{242}$Pu: True ternary fission and Tin-accompanied ternary fission of $^{242}$Pu are\nstudied by using Three Cluster Model. True ternary fission is considered as\nformation of heavy fragments in the region $28\\leq Z_1,Z_2,Z_3\\leq 38$, with\ncomparable masses. The possible fission channels are predicted from\npotential-energy calculations. Interaction potentials, Q-values and relative\nyields for all possible fragmentations in equatorial and collinear\nconfigurations are calculated and compared to each other. It is found out that\nternary fission with formation of a double magic nucleus like $^{132}Sn$ is\nmore probable than the other fragmentations. Also the kinetic energies of the\nfragments for the group $Z_1=32$, $Z_2=32$ and $Z_3=30$ are calculated for all\ncombinations in the collinear geometry, as a sequential decay.", "category": "nucl-th" }, { "text": "Entanglement Maximization in Low-Energy Neutron-Proton Scattering: The entanglement properties of neutron-proton scattering are investigated\nusing a measure that counts the number of entangled pairs produced by the\naction of a scattering operator on a given initial neutron-proton state. All\nphase shifts relevant for scattering at laboratory energies up to 350 MeV are\nused.\n Entanglement is found to be maximized in very low energy scattering. At such\nenergies the Hamiltonian obeys Wigner SU(4) symmetry, and an entanglement\nmaximum is a sign of that symmetry. At higher energies the angular dependence\nof entanglement is strong and the entanglement is large for many scattering\nangles. The tensor force is shown to play a significant role in producing\nentanglement at lab kinetic energies greater than about 50 MeV.", "category": "nucl-th" }, { "text": "Improved microscopic-macroscopic approach incorporating the effects of\n continuum states: The Woods-Saxon-Strutinsky method (the microscopic-macroscopic method)\ncombined with Kruppa's prescription for positive energy levels, which is\nnecessary to treat neutron rich nuclei, is studied to clarify the reason for\nits success and to propose improvements for its shortcomings. The reason why\nthe plateau condition is met for the Nilsson model but not for the Woods-Saxon\nmodel is understood in a new interpretation of the Strutinsky smoothing\nprocedure as a low-pass filter. Essential features of Kruppa's level density is\nextracted in terms of the Thomas-Fermi approximation modified to describe\nspectra obtained from diagonalization in truncated oscillator bases. A method\nis proposed which weakens the dependence on the smoothing width by applying the\nStrutinsky smoothing only to the deviations from a reference level density. The\nBCS equations are modified for the Kruppa's spectrum, which is necessary to\ntreat the pairing correlation properly in the presence of continuum. The\npotential depth is adjusted for the consistency between the microscopic and\nmacroscopic Fermi energies. It is shown, with these improvements, that the\nmicroscopic-macroscopic method is now capable to reliably calculate binding\nenergies of nuclei far from stability.", "category": "nucl-th" }, { "text": "Fluctuations in the number of intermediate mass fragments in small\n projectile like fragments: The origin of fluctuations in the average number of intermediate mass\nfragments seen in experiments in small projectile like fragments is discussed.\nWe argue that these can be explained on the basis of a recently proposed model\nof projectile fragmentation.", "category": "nucl-th" }, { "text": "Metric anisotropies and nonequilibrium attractor for expanding plasma: We consider the evolution of a system of chargeless and massless particles in\nan anisotropic space-time given by the Bianchi type I metric. Specializing to\nthe axis-symmetric case, we derive the framework of anisotropic hydrodynamics\nfrom the Boltzmann equation in the relaxation-time approximation. We consider\nthe case of the axis-symmetric Kasner metric and study the approach to the\nemergent attractor in near and far-off-equilibrium regimes. Further, by\nrelaxing the Kasner conditions on metric coefficients, we study the effect of\nexpansion geometries on the far-off-equilibrium attractor and discuss its\nimplications in the context of relativistic heavy-ion collisions.", "category": "nucl-th" }, { "text": "From Kuo-Brown to today's realistic shell-model calculations: This paper is an homage to the seminal work of Gerry Brown and Tom Kuo, where\nshell model calculations were performed for 18O and 18F using an effective\ninteraction derived from the Hamada-Johnston nucleon-nucleon potential. That\nwork has been the first successful attempt to provide a description of nuclear\nstructure properties starting from the free nucleon-nucleon potential. We shall\ncompare the approach employed in the 1966 paper with the derivation of a modern\nrealistic shell-model interaction for sd-shell nuclei, evidencing the progress\nthat has been achieved during the last decades.", "category": "nucl-th" }, { "text": "On a variational principle model for the Nuclear Caloric curve: Following the lead of a recent work we perform a variational principle model\ncalculation for the nuclear caloric curve. A Skyrme type interaction with and\nwithout momentum dependence is used. The calculation is done for a large\nnucleus, i.e, in the nuclear matter limit. Thus we address the issue of volume\nfragmentation only. Nonetheless the results are similar to the previous,\nlargely phenomenological calculation for a finite nucleus. We find the onset of\nfragmentation can be sudden as a function of temperature/excitation energy.", "category": "nucl-th" }, { "text": "Pairing effects on spinodal decomposition of asymmetric nuclear matter: We investigate the impact of pairing correlations on the behavior of unstable\nasymmetric nuclear matter at low temperature. We focus on the relative role of\nthe pairing interaction, coupling nucleons of the same type (neutrons or\nprotons), with respect to the symmetry potential, which enhances the\nneutron-proton attraction, along the clusterization process driven by spinodal\ninstabilities. It is found that, especially at the transition temperature from\nthe normal to the superfluid phase, pairing effects may induce significant\nvariations in the isotopic content of the clusterized matter. This analysis is\npotentially useful to gather information on the temperature dependence of\nnuclear pairing and, in general, on the properties of clusterized low-density\nmatter, of interest also in the astrophysical context.", "category": "nucl-th" }, { "text": "Effect of liquid drop model parameters on nuclear liquid gas phase\n transition: The phenomenon of liquid-gas phase transition occurring in heavy ion\ncollisions at intermediate energies is a subject of contemporary interest. In\nstatistical models of fragmentation, the liquid drop model is generally used to\ncalculate the ground state binding energies of the fragments. It is well known\nthat the surface and symmetry energy of the hot fragments at the low density\nfreeze out can be considerably modified. In addition to this, the level density\nparameter also has a wide variation. The effect of variation of these\nparameters is studied on fragmentation observables which are related to the\nnuclear liquid gas phase transition. The canonical thermodynamical model which\nhas been very successful in describing the phenomenon of fragmentation is used\nfor the study. The shift in transition temperature owing to the variation in\nliquid drop model parameters has been examined.", "category": "nucl-th" }, { "text": "Two-particle correlations at high-energy nuclear collisions,\n peripheral-tube model revisited: In this paper, we give an account of the peripheral-tube model, which has\nbeen developed to give an intuitive and dynamical description of the so-called\nridge effect in two-particle correlations in high-energy nuclear collisions.\nStarting from a realistic event-by-event fluctuating hydrodynamical model\ncalculation, we first show the emergence of ridge + shoulders in the so-called\ntwo-particle long-range correlations, reproducing the data. In contrast to the\ncommonly used geometric picture of the origin of the anisotropic flow, we can\nexplain such a structure dynamically in terms of the presence of high\nenergy-density peripheral tubes in the initial conditions. These tubes\nviolently explode and deflect the near radial flow coming from the interior of\nthe hot matter, which in turn produces a two-ridge structure in single-particle\ndistribution, with approximately two units opening in azimuth. When computing\nthe two-particle correlation, this will result in characteristic three-ridge\nstructure, with a high near-side ridge and two symmetric lower away-side ridges\nor shoulders. Several anisotropic flows, necessary to producing ridge +\nshoulder structure, appear naturally in this dynamical description. Using this\nsimple idea, we can understand several related phenomena, such as centrality\ndependence and trigger-angle dependence.", "category": "nucl-th" }, { "text": "Dynamics of rotation in chiral nuclei: The dynamics of chiral nuclei is investigated for the first time with the\ntime-dependent and tilted axis cranking covariant density functional theories\non a three-dimensional space lattice in a microscopic and self-consistent way.\nThe experimental energies of the two pairs of the chiral doublet bands in\n$^{135}$Nd are well reproduced without any adjustable parameters beyond the\nwell-defined density functional. A novel mechanism, i.e., chiral precession, is\nrevealed from the microscopic dynamics of the total angular momentum in the\nbody-fixed frame, whose harmonicity is associated with a transition from the\nplanar into aplanar rotations with the increasing spin. This provides a fully\nmicroscopic and dynamical view to understand the chiral excitations in nuclei.", "category": "nucl-th" }, { "text": "Symmetry preserving truncations of the gap and Bethe-Salpeter equations: Ward-Green-Takahashi (WGT) identities play a crucial role in hadron physics,\ne.g. imposing stringent relationships between the kernels of the one- and\ntwo-body problems, which must be preserved in any veracious treatment of mesons\nas bound-states. In this connection, one may view the dressed gluon-quark\nvertex, $\\Gamma_\\mu^a$, as fundamental. We use a novel representation of\n$\\Gamma_\\mu^a$, in terms of the gluon-quark scattering matrix, to develop a\nmethod capable of elucidating the unique quark-antiquark Bethe-Salpeter kernel,\n$K$, that is symmetry-consistent with a given quark gap equation. A strength of\nthe scheme is its ability to expose and capitalise on graphic symmetries within\nthe kernels. This is displayed in an analysis that reveals the origin of\n$H$-diagrams in $K$, which are two-particle-irreducible contributions,\ngenerated as two-loop diagrams involving the three-gluon vertex, that cannot be\nabsorbed as a dressing of $\\Gamma_\\mu^a$ in a Bethe-Salpeter kernel nor\nexpressed as a member of the class of crossed-box diagrams. Thus, there are no\ngeneral circumstances under which the WGT identities essential for a valid\ndescription of mesons can be preserved by a Bethe-Salpeter kernel obtained\nsimply by dressing both gluon-quark vertices in a ladder-like truncation; and,\nmoreover, adding any number of similarly-dressed crossed-box diagrams cannot\nimprove the situation.", "category": "nucl-th" }, { "text": "Chiral properties of hadron correlators in nuclear matter: The constraints imposed by chiral symmetry on hadron correlation functions in\nnuclear medium are discussed. It is shown that these constraints imply a\ncertain structure for the in-medium hadron correlators and lead to the\ncancelation of the order $\\rho m_\\pi$ term in the in-medium nucleon correlator.\nWe also consider the effect of mixing of the chiral partners correlation\nfunctions arising from the interaction of nuclear pions with corresponding\ninterpolating currents. It reflects the phenomena of partial restoration of\nchiral symmetry. The different scenarios of such restoration are briefly\ndiscussed.", "category": "nucl-th" }, { "text": "Freezeout systematics due to the hadron spectrum: We investigate systematics of the freezeout surface in heavy ion collisions\ndue to the hadron spectrum. The role of suspected resonance states that are yet\nto be confirmed experimentally in identifying the freezeout surface has been\ninvestigated. We have studied two different freezeout schemes - unified\nfreezeout scheme where all hadrons are assumed to freezeout at the same thermal\nstate and a flavor dependent sequential freezeout scheme with different\nfreezeout thermal states for hadrons with or without valence strange quarks.\nThe data of mean hadron yields as well as scaled variance of net proton and net\ncharge distributions have been analysed. We find the freezeout temperature $T$\nto drop by $\\sim5\\%$ while the dimensionless freezeout parameters $\\mu_B/T$ and\n$VT^3$ ($\\mu_B$ and $V$ are the baryon chemical potential and the volume at\nfreezeout respectively) are insensitive to the systematics of the input hadron\nspectrum. The observed hint of flavor hierarchy in $T$ and $VT^3$ with only\nconfirmed resonances survives the systematics of the hadron spectrum. It is\nmore prominent between $\\sqrt{s_{NN}}\\sim10 - 100$ GeV where the maximum\nhierarchy in $T\\sim10\\%$ and $VT^3\\sim40\\%$. However, the uncertainties in the\nthermal parameters due to the systematics of the hadron spectrum and their\ndecay properties do not allow us to make a quantitative estimate of the flavor\nhierarchy yet.", "category": "nucl-th" }, { "text": "Bohr Hamiltonian with Hulthen plus ring-shaped potential for triaxial\n nuclei with deformation-dependent mass term: In this work, we present a new version of the Bohr collective Hamiltonian for\ntriaxial nuclei within Deformation-Dependent Mass formalism (DDM) using the\nHulth\\'en potential. We shall call the developed model Z(5)-HD. Analytical\nexpressions for energy spectra are derived by means of the recent version of\nthe Asymptotic Iteration Method. The calculated numerical results of energies\nand B(E2) transition rates are compared with the experimental data, and several\ntheoretical results from Z(5) model, the model Z(5)-H using the Hulth\\'en\npotential without DDM formalism as well as theoretical predictions of Z(5)-DD\nmodel with Davidson potential using DDM formalism. The obtained results show an\noverall agreement with experimental data and an important improvement in\nrespect to the other models.", "category": "nucl-th" }, { "text": "On the nuclear interaction. Potential, binding energy and fusion\n reaction: The nuclear interaction is responsible for keeping neutrons and protons\njoined in an atomic nucleus. Phenomenological nuclear potentials, fitted to\nexperimental data, allow one to know about the nuclear behaviour with more or\nless success where quantum mechanics is hard to be used. A nuclear potential is\nsuggested and an expression for the potential energy of two nuclear entities,\neither nuclei or nucleons, is developed. In order to estimate parameters in\nthis expression, some nucleon additions to nuclei are considered and a model is\nsuggested as a guide of the addition process. Coulomb barrier and energy for\nthe addition of a proton to each one of several nuclei are estimated by taking\ninto account both the nuclear and electrostatic components of energy. Studies\non the binding energies of several nuclei and on the fusion reaction of two\nnuclei are carried out.", "category": "nucl-th" }, { "text": "Averaged transverse momentum correlations of hadrons in relativistic\n heavy-ion collisions: We compile experimental data for the averaged transverse momentum\n($\\left\\langle p_{T}\\right\\rangle $) of proton, $\\Lambda$, $\\Xi^{-}$,\n$\\Omega^{-}$ and $\\phi$ at mid-rapidity in Au+Au collisions at $\\sqrt{s_{NN}}=$\n200, 39, 27, 19.6, 11.5, 7.7 GeV and in Pb+Pb collisions at $\\sqrt{s_{NN}}=$\n2.76 TeV, and find that experimental data of these hadrons exhibit systematic\ncorrelations. We apply a quark combination model with equal-velocity\ncombination approximation to derive analytic formulas of hadronic $\\left\\langle\np_{T}\\right\\rangle $ in the case of exponential form of quark $p_{T}$ spectra\nat hadronization. We use them to successfully explain the systematic\ncorrelations exhibited in $\\left\\langle p_{T}\\right\\rangle $ data of\n$p\\Lambda$, $\\Lambda\\Xi^{-}$, $\\Xi^{-}\\Omega^{-}$ and $\\Xi^{-}\\phi$ pairs. We\nalso use them to successfully explain the regularity observed in $\\left\\langle\np_{T}\\right\\rangle $ of these hadrons as the function of\n$(dN_{ch}/dy)/(N_{part}/2)$ at mid-rapidity in central heavy-ion collisions at\nboth RHIC and LHC energies. Our results suggest that the constituent quark\ndegrees of freedom and the equal-velocity combination of these constituent\nquarks at hadronization play important role in understanding the production of\nbaryons and $\\phi$ meson at these RHIC and LHC energies.", "category": "nucl-th" }, { "text": "Spinodal Instability at the Onset of Collective Expansion in Nuclear\n Collisions: Using transport theory to model central Au + Au collisions in the energy\nregion of 20 - 110 MeV/u, at impact parameters b <= 5 fm, we predict a\nmeasurable impact of spinoidal instability as the collective expansion sets in\nwith energy. Two transport models are employed, the pBUU model, solving a\nBoltzmann-Uehling-Uhlenbeck equation, and the Brownian Motion (BM) model,\nsolving a set of Langevin equations to describe the motion of individual\nnucleons in a noisy nuclear medium. We find without ambiguity, for the first\ntime, that a combination of delayed equilibration, onset of collective\nexpansion and the spinodal instability produces a pair of transient ring\nstructures, made of the projectile and target remnants, with spectator nucleons\npredicted to end in the entities reminiscent of stones in jewelry, on the\nrings. The ring structures, calculated in the configuration space and mapped\nonto the velocity space, could be detected in experimental collective flow\ndata.", "category": "nucl-th" }, { "text": "Effects of the Lorentz invariance violation in Coulomb interaction in\n nuclei and atoms: Anisotropy in the speed of light that has been constrained by\nMichelson-Morley-type experiments also generates anisotropy in the Coulomb\ninteractions. This anisotropy can manifest itself as an energy anisotropy in\nnuclear and atomic experiments. Here the experimental limits on Lorentz\nviolation in 21Ne are used to improve the limits on the Lorentz symmetry in the\nphoton sector, namely the anisotropy of the speed of light and the Coulomb\ninteractions, by 7 orders of magnitude in comparison with previous experiments:\nthe speed of light is isotropic to a part in E-28.", "category": "nucl-th" }, { "text": "Does the quark cluster model predict any isospin two dibaryon resonance?: We analyze the possible existence of a resonance in the $J^P=0^-$ channel\nwith isospin two by means of nucleon-$\\Delta$ interactions based on the\nconstituent quark model. We solve the bound state and the scattering problem\nusing two different potentials, a local and a non-local one. The non-local\npotential results to be the more attractive, although not enough to generate\nthe experimentally predicted resonance.", "category": "nucl-th" }, { "text": "Simultaneous Optical Model Analyses of Elastic Scattering, Breakup, and\n Fusion Cross Section Data for the $^{6}$He + $^{209}$Bi System at\n Near-Coulomb-Barrier Energies: Based on an approach recently proposed by us, simultaneous\n$\\chi^{2}$-analyses are performed for elastic scattering, direct reaction (DR)\nand fusion cross sections data for the $^{6}$He+$^{209}$Bi system at\nnear-Coulomb-barrier energies to determine the parameters of the polarization\npotential consisting of DR and fusion parts. We show that the data are well\nreproduced by the resultant potential, which also satisfies the proper\ndispersion relation. A discussion is given of the nature of the threshold\nanomaly seen in the potential.", "category": "nucl-th" }, { "text": "Band-like structures and quartets in deformed N=Z nuclei: We provide a description of deformed $N=Z$ nuclei in a formalism of\n$\\alpha$-like quartets. Quartets are constructed variationally by resorting to\nthe use of proper intrinsic states. Various types of intrinsic states are\nintroduced which generate different sets of quartets for a given nucleus.\nEnergy spectra are generated via configuration-iteraction calculations in the\nspaces built with these quartets. The approach has been applied to $^{24}$Mg\nand $^{28}$Si in the $sd$ shell and to $^{48}$Cr in the $pf$ shell. In all\ncases a good description of the low-lying spectra has been achieved. As a\npeculiarity of the approach, a close correspondence is observed between the\nvarious sets of quartets employed and the occurrence of well defined band-like\nstructures in the spectra of the systems under study.", "category": "nucl-th" }, { "text": "Exotic Shapes in ^{32}S suggested by the Symmetry-Unrestricted Cranked\n Hartree-Fock Calculations: High-spin structure of ^{32}S is investigated by means of the cranked\nSkyrme-Hartree-Fock method in the three-dimensional Cartesian-mesh\nrepresentation. Some interesting suggestions are obtained: 1) An internal\nstructure change (toward hyperdeformation) may occur at I>20 in the\nsuperdeformed band, 2) A non-axial Y_{31} deformed band may appear in the yrast\nline with 4 n n gamma, p-wave pion production in NN collisions, tritium beta decay, pp\nfusion, nu d scattering, and the hep reaction. Using a Gamow-Teller matrix\nelement obtained from calculations of pp fusion as input we compute the neutron\nspectrum obtained in pi- d -> n n gamma. With the short-distance physics in\nthis process controlled from p p -> d e+ nu_e the theoretical uncertainty in\nthe nn scattering length extracted from pi- d -> n n gamma is reduced by a\nfactor larger than three, to <~0.05 fm.", "category": "nucl-th" }, { "text": "Hard probes in isobar collisions as a probe of the neutron skin: We present an estimate of the yield of hard probes expected for collisions of\nthe isobars $^{96}_{44}$Ru and $^{96}_{40}$Zr at collision energies reachable\nat RHIC and the LHC\\@. These yields are proportional to the number of binary\nnucleon-nucleon interactions, which is characteristically different due to the\npresence of the large neutron skin in $^{96}_{40}$Zr. This provides an\nindependent opportunity to measure the difference between the neutron skin of\n$^{96}_{44}$Ru and $^{96}_{40}$Zr, which can provide an important constraint on\nthe Equation of State of cold neutron-rich matter.", "category": "nucl-th" }, { "text": "CFNS Ad-Hoc meeting on Radiative Corrections Whitepaper: Current precision scattering experiments and even more so many experiments\nplaned for the Electron Ion Collider will be limited by systematics. From the\ntheory side, a fundamental source of systematic uncertainty is the correct\ntreatment of radiative effects. To gauge the current state of technique and\nknowledge, help the cross-pollination between different direction of nuclear\nphysics, and to give input to the yellow report process, the community met in\nan ad-hoc workshop hosted by the Center for Frontiers in Nuclear Science, Stony\nBrook University. This whitepaper is a collection of contributions to this\nworkshop.", "category": "nucl-th" }, { "text": "Dynamics of light hypernuclei in collisions of $^{197}$Au+$^{197}$Au at\n GeV energies: The dynamics of light hypernuclei and nuclear clusters produced in\n$^{197}$Au+$^{197}$Au collisions has been investigated thoroughly with a\nmicroscopic transport model. All possible channels of hyperon production and\ntransportation of hyperons in nuclear medium are implemented into the model.\nThe light complex fragments are recognized with the Wigner density approach at\nthe stage of freeze out in nuclear collisions. The isospin diffusion in the\ncollisions is responsible for the neutron-rich cluster formation. The\ncollective flows of nuclear clusters are consistent with the experimental data\nfrom FOPI collaboration. It is found that the influence of the hyperon-nucleon\npotential on the free hyperons is negligible, but available for the light\nhypernuclide formation. The directed and elliptic flows of $^{3}_{\\Lambda}$H\nand $^{4}_{\\Lambda}$H at incident energies of 2, 2.5, 3, 3.5 and 4 GeV/nucleon\nare investigated thoroughly and manifest the same structure with the nuclear\nclusters. The hypernuclear yields are produced in a wide rapidity and momentum\nregime with increasing the beam energy.", "category": "nucl-th" }, { "text": "The Local Potential Approximation for the Brueckner G-matrix: The Brueckner G-matrix for a slab of nuclear matter is analyzed in the\nsinglet $^1S$ and triplet $^3S+^3D$ channels. The complete Hilbert space is\nsplit into two domains, the model subspace $S_0$, in which the two-particle\npropagator is calculated explicitly, and the complementary one, $S'$, in which\nthe local potential approximation is used. This kind of local approximation was\npreviously found to be quite accurate for the $^1S$ pairing problem. A set of\nmodel spaces $S_0(E_0)$ with different values of the cut-off energy $E_0$ is\nconsidered, $E_0$ being the upper limit for the single-particle energies of the\nstates belonging to $S_0$. The independence of the G-matrix of $E_0$ is assumed\nas a criterion of validity of the local potential approximation. Such\nindependence is obtained within few percent for $E_0=10 \\div 20$ MeV for both\nthe channels under consideration.", "category": "nucl-th" }, { "text": "Theta+ formation in inclusive gamma D -> pK- X: We analyze the possibility to produce an intermediate Theta^+ via a\nKN->\\Theta+ formation process in gamma D-> pK^- X (X=nK^+,pK^0) reactions at\nsome specific kinematical conditions, in which a pK^- pair is knocked out in\nthe forward direction and its invariant mass is close to the mass of\nLambda(1520). The \\Theta^+ signal may appear in the [\\gamma D,pK^-] missing\nmass distribution. The ratio of the signal (cross section at the \\Theta^+ peak\nposition) to the smooth background processes varies from 0.7 to 2.5 depending\non the spin and parity of Theta+, and it decreases correspondingly if the pK^-\ninvariant mass is outside of the Lambda(1520)-resonance region. We analyze the\nrecent CLAS search for the Theta+ in the gamma D ->pK^-nK^+ reaction and show\nthat the conditions of this experiment greatly reduce the Theta+ formation\nprocess making it difficult to extract a Theta+ peak from the data.", "category": "nucl-th" }, { "text": "Study of the $J/\u03c8\\to \u03c6(\u03c9) f_2(1270)$, $J/\u03c8\\to \u03c6\n (\u03c9) f'_2(1525)$ and $J/\u03c8\\to K^{*0}(892) \\bar{K}^{* 0}_2(1430)$\n decays: We present an approach to study the decay modes of the $J/\\psi$ into a vector\nmeson and a tensor meson, taking into account the nature of the $f_2(1270)$,\n$f'_2(1525)$, $\\bar{K}^{* 0}_2(1430)$ resonances as dynamically generated\nstates from the vector meson-vector meson interaction. We evaluate four ratios\nof partial decay widths in terms of a flavor dependent OZI breaking parameter\nand the results obtained compare favorably with experiment. The fit to the data\nis possible due to the particular strength and sign of the couplings of the\nresonances to pairs of vector mesons given by the theory, thus providing a\nnontrivial test for the idea of these tensor states as dynamically generated\nfrom the vector-vector interaction.", "category": "nucl-th" }, { "text": "Proxy-$SU(4)$ symmetry in A=60-90 region: Applications of the proxy-$SU(3)$ model of Bonatsos and collaborators to\nnuclei in A=60-90 region introduces proxy-$SU(4)$ symmetry. Shell model spaces\nwith single particle (sp) orbits $^1p_{3/2}$, $^1p_{1/2}$, $^0f_{5/2}$ and\n$^0g_{9/2}$ are essential for these nuclei and also protons and neutrons in\nthis region occupy the same sp orbits. With this and applying the \"proxy\nscheme\", the $^0g_{9/2}$ changes to $^0f_{7/2}$ giving the SGA $U(40) \\supset\n[U(10) \\supset G \\supset SO(3)] \\otimes [SU(4) \\supset SU_S(2) \\otimes\nSU_T(2)]$. With $G=SU(3)$, we have the proxy-$SU(3)$ model. It is easy to see\nthat proxy-$SU(3)$ symmetry implies goodness of the $SU(4)$ symmetry appearing\nabove, i.e. proxy-$SU(4)$ symmetry. Shell model calculations pointing out the\nneed for $^0g_{9/2}$ orbit, ground state masses, shape changes and shape\nco-existence in A=60-90 region and GT distributions clearly show the importance\nof proxy-$SU(4)$ in this mass region. Besides presenting this evidence, new\nproxy schemes with $G=SU(5)$, $SO(6)$ and $SO(10)$ that are generated by good\nproxy-$SU(4)$ symmetry are described in some detail. An important feature is\nthat the four proxy symmetries $SU(3)$, $SO(6)$, $SU(5)$ and $SO(10)$ appear\ntwice.", "category": "nucl-th" }, { "text": "Isovector dipole-resonance structure within the effective surface\n approximation: The nuclear isovector-dipole strength structure is analyzed in terms of the\nmain and satellite (pygmy) peaks within the Fermi-liquid droplet model. Such a\nstructure is sensitive to the value of the surface symmetry-energy constant\nobtained analytically for different Skyrme forces in the leptodermous effective\nsurface approximation. Energies, sum rules and transition densities of the main\nand satellite peaks for specific Skyrme forces are qualitatively in agreement\nwith the experimental data and other theoretical calculations.", "category": "nucl-th" }, { "text": "Photoproduction of the Lambda(1405) on the proton and nuclei: We study the gamma p ---> K^+ Lambda(1405) reaction at energies close to\nthreshold using a chiral unitary model where the resonance is generated\ndynamically from K^-p interaction with other channels constructed from the\noctets of baryons and mesons. Predictions are made for cross sections into\nseveral channels and it is shown that the detection of the K^+ is sufficient to\ndetermine the shape and strength of the Lambda(1405) resonance. The\ndetermination of the resonance properties in nuclei requires instead the\ndetection of the resonance decay channels. Pauli blocking effects on the\nresonance, which have been shown to be very important for the resonance at rest\nin the nucleus, are irrelevant here where the resonance is produced with a\nlarge momentum. The nuclear modifications here would thus offer information on\nthe resonance and K^- nucleus dynamics complementary to the one offered so far\nby K^- atoms.", "category": "nucl-th" }, { "text": "Systematic analysis of hadron spectra in p+p collisions using Tsallis\n distribution: Using the experimental data from the STAR, PHENIX, ALICE and CMS programs on\nthe rapidity and energy dependence of the $p_T$ spectra in p+p collisions, we\nshow that a universal distribution exists. The energy dependence of temperature\n$T$ and parameter $n$ of the Tsallis distribution are also discussed in detail.\nA cascade particle production mechanism in p+p collisions is proposed.", "category": "nucl-th" }, { "text": "Clustering effects in the $^6$Li(p,$^3$He)$^4$He reaction at\n astrophysical energies: Background: The understanding of nuclear reactions between light nuclei at\nenergies below the Coulomb barrier is important for several astrophysical\nprocesses, but their study poses experimental and theoretical challenges. At\nsufficiently low energies, the electrons surrounding the interacting ions\naffect the scattering process. Moreover, the clustered structure of some of\nthese nuclei may play a relevant role on the reaction observables.\n Purpose: In this article, we focus on a theoretical investigation of the role\nof clustered configurations of $^6$Li in reactions of astrophysical interest.\n Methods: The $^6$Li(p,$^3$He)$^4$He reaction cross section is described\nconsidering both the direct transfer of a deuteron as a single point-like\nparticle in Distorted Wave Born Approximation (DWBA), and the transfer of a\nneutron and a proton in second-order DWBA. A number of two- and three-cluster\nstructure models for $^6$Li are compared.\n Results: Within the two-cluster structure model, we explore the impact of the\ndeformed components in the $^6$Li wave-function on the reaction of interest.\nWithin the three-cluster structure model, we gauge the degree of $\\alpha$-d\nclustering and explicitly probe its role on specific features of the reaction\ncross section. We compare the energy trend of the astrophysical $S$ factor\ndeduced in each case.\n Conclusions: Clustered $^6$Li configurations lead in general to a significant\nenhancement of the astrophysical factor in the energy region under study. This\neffect only originates from clustering, whereas static deformations of the\nground-state configuration play a negligible role at very low energies.", "category": "nucl-th" }, { "text": "A Chiral Mean-Field Equation-of-State in UrQMD: Effects on the Heavy Ion\n Compression Stage: It is shown that the initial compression in central heavy ion collisions at\nbeam energies of $E_\\mathrm{lab}=1-10A$~GeV depends dominantly on the\nunderlying equation of state and only marginally on the model used for the\ndynamical description. To do so, a procedure to incorporate any equation of\nstate in the UrQMD transport model is introduced. In particular we compare the\nbaryon density, temperature and pressure evolution as well as produced entropy\nin a relativistic ideal hydrodynamics approach and the UrQMD transport model,\nwhere the same equation of state is used in both approaches. Not only is the\ncompression similar if the same equation of state is used in either dynamical\nmodel, but it also strongly depends on the actual equation of state. These\nresults indicate that the equation of state can be studied with observables\nwhich are sensitive to the initial compression phase and maximum compression\nachieved in heavy ion collisions at these beam energies.", "category": "nucl-th" }, { "text": "Generalized entropy and temperature in nuclear multifragmentation: In the framework of a 2D Vlasov model, we study the time evolution of the\n\"coarse-grained\" Generalized Entropy (GE) in a nuclear system which undergoes a\nmultifragmentation (MF) phase transition. We investigate the GE both for the\ngas and the fragments (surface and bulk part respectively). We find that the\nformation of the surface causes the growth of the GE during the process of\nfragmentation. This quantity then characterizes the MF and confirms the crucial\nrole of deterministic chaos in filling the new available phase-space: at\nvariance with the exact time evolution, no entropy change is found when the\nlinear response is applied. Numerical simulations were used also to extract\ninformation about final temperatures of the fragments. From a fitting of the\nmomentum distribution with a Fermi-Dirac function we extract the temperature of\nthe fragments at the end of the process. We calculate also the gas temperature\nby averaging over the available phase space. The latter is a few times larger\nthan the former, indicating a gas not in equilibrium. Though the model is very\nschematic, this fact seems to be very general and could explain the discrepancy\nfound in experimental data when using the slope of light particles spectra\ninstead of the double ratio of isotope yields method in order to extract the\nnuclear caloric curve.", "category": "nucl-th" }, { "text": "Application of the coherent density fluctuation model to study the\n nuclear matter properties of finite nuclei within the relativistic mean-field\n formalism: We obtained a density-dependent analytical expression of binding energy per\nnucleon for different neutron-proton asymmetry of the nuclear matter (NM) with\na polynomial fitting, which manifests the results of effective field theory\nmotivated relativistic mean-field (E-RMF) model. This expression has the edge\nover the Br$\\ddot{u}$ckner energy density functional [Phys. Rev. {\\bf 171},\n1188 (1968)] since it resolves the Coster-Band problem. The NM parameters like\nincompressibility, neutron pressure, symmetry energy, and its derivatives are\ncalculated using the acquired expression of energy per nucleon. Further, the\nweight function calculated by E-RMF densities are folded with calculated NM\nparameters within coherent density fluctuation model to find the properties of\nclosed/semi-closed-shell even-even $^{16}$O, $^{40}$Ca, $^{48}$Ca, $^{56}$Ni,\n$^{90}$Zr, $^{116}$Sn, and $^{208}$Pb nuclei. The values obtained for the\nneutron pressure $P^{A}$, symmetry energy $S^{A}$ and its derivative\n$L_{sym}^A$ known as slope parameter, lie within a narrow domain whereas there\nis a large variation in isoscalar incompressibility $K^{A}$ and surface\nincompressibility $K_{sym}^{A}$ while moving from light to heavy nuclei. The\nsizable variation in $K^{A}$ and $K_{sym}^{A}$ for light and heavy nuclei\ndepicts their structural dependence due to the peculiar density distribution of\neach nucleus. A comparison of surface quantities calculated in the present work\nhas also been made with ones obtained via Br$\\ddot{u}$ckner energy density\nfunctional.", "category": "nucl-th" }, { "text": "Theoretical analysis of $^8$Li + $^{208}$Pb reaction and the critical\n angular momentum for complete fusion: In a theoretical approach, the complete and incomplete fusions are\ninvestigated by considering the $^8$Li+$^{208}$Pb reaction. By decreasing the\nprojectile ground-state binding energy $\\varepsilon_b$ from its known\nexperimental value, the complete fusion is shown to have insignificant\ndependence on such variations, whereas the incomplete fusion strongly depends\non that. The complete and incomplete fusion cross sections are calculated by\nusing a combination of both continuum-discretized coupled-channel and sum-rule\nmodels. To this end, an incident-energy dependent cut-off angular momentum\n$L_c$ is first obtained by using the available complete fusion experimental\ndata, within an approach which is extended to model results obtained for other\nincident-energies. An approximated fitted expression linking $L_c$ to the\nwell-known critical value $L_{\\rm crit}$ derived by Wilczy\\'nski [Nucl. Phys. A\n216 (1973) 386] suggests a generalization of the corresponding sum-rule model\nto energies around and below the Coulomb barrier.", "category": "nucl-th" }, { "text": "Pseudo-Spin Symmetry and its Applications: The pseudo-spin symmetry is reviewed. A mapping that produces the separation\nof the total angular momentum into pseudo-orbital and pseudo-spin degrees of\nfreedom is discussed, together with the analytic transformations that take us\nfrom the normal parity space to the eigenstates of a pseudo-oscillator with one\nquanta less. The many-particle version of the unitary transformation to the\npseudo-SU(3) space is established. As an example, these symmetries are used to\ndescribe the double beta decay phenomenon in heavy deformed nuclei.", "category": "nucl-th" }, { "text": "Cronin effect from backward to forward rapidity: I discuss recent experimental data on the Cronin effect in deuteron-gold\ncollisions at the top RHIC energy, in a pseudorapidity range [-2,3]. Two\ntheoretical approaches are compared and contrasted: the pQCD-based\nGlauber-Eikonal model and Colour Glass Condensate models. Neither can describe\nthe Cronin effect over the whole pseudorapidity interval up to now explored\nexperimentally, its most mysterious and intriguing part being at negative\nrapidity.", "category": "nucl-th" }, { "text": "Covariant kinetic freeze out description through a finite space-time\n layer: We develop and analyze a covariant FO probability valid for a finite\nspace-time layer.", "category": "nucl-th" }, { "text": "Neutron star mass formula with nuclear saturation parameters for\n asymmetric nuclear matter: Low-mass neutron stars are directly associated with the nuclear saturation\nparameters because their central density is definitely low. We have already\nfound a suitable combination of nuclear saturation parameters for expressing\nthe neutron star mass and gravitational redshift, i.e., $\\eta\\equiv\n(K_0L^2)^{1/3}$ with the incompressibility for symmetric nuclear matter, $K_0$,\nand the density-dependent nuclear symmetry energy, $L$. In this study, we newly\nfind another suitable combination given by $\\eta_\\tau\\equiv (-K_\\tau\nL^5)^{1/6}$ with the isospin dependence of incompressibility for asymmetric\nnuclear matter, $K_\\tau$, and derive the empirical relations for the neutron\nstar mass and gravitational redshift as a function of $\\eta_\\tau$ and the\nnormalized central number density. With these empirical relations, one can\nevaluate the mass and gravitational redshift of the neutron star, whose central\nnumber density is less than threefold the saturation density, within $\\sim\n10\\%$ accuracy, and the radius within a few \\% accuracies. In addition, we\ndiscuss the neutron star mass and radius constraints from the terrestrial\nexperiments, using the empirical relations, together with those from the\nastronomical observations. Furthermore, we find a tight correlation between\n$\\eta_\\tau$ and $\\eta$. With this correlation, we derive the constraint on\n$K_\\tau$ as $-348\\le K_\\tau\\le -237$ MeV, assuming that $L=60\\pm 20$ and\n$K_0=240\\pm 20$ MeV.", "category": "nucl-th" }, { "text": "Role of magnetic fields on the outer crust in a magnetar: We explore the properties of 4110 nuclides from Z = 5 to Z = 82 with the\nSky3D code and the composition of the outer crust in the magnetars under\nextreme magnetic fields. The effects of the variation of the nuclear masses due\nto the magnetic fields on the outer crust are comprehensively studied. The\nneutron-drip transition pressure, the equation of state and neutron fraction in\nthe outer crust have also been discussed.", "category": "nucl-th" }, { "text": "Multipole expansion of densities in the deformed relativistic\n Hartree-Bogoliubov theory in continuum: The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) has\nbeen proved one of the best models to probe the exotic structures in deformed\nnuclei. In DRHBc, the potentials and densities are expressed in terms of the\nmultipole expansion with Legendre polynomials, the dependence on which has only\nbeen touched for light nuclei so far. In this paper, taking a light nucleus\n$^{20}$Ne and a heavy nucleus $^{242}$U as examples, we investigated the\ndependence on the multipole expansion of the potentials and densities in DRHBc.\nIt is shown that the total energy converges well with the expansion truncation\nboth in the absence of and presence of the pairing correlation, either in the\nground state or at a constrained quadrupole deformation. It is found that to\nreach a same accuracy of the total energy, even to a same relative accuracy by\npercent, a larger truncation is required by a heavy nucleus than a light one.\nThe dependence of the total energy on the truncation increases with\ndeformation. By decompositions of the neutron density distribution, it is shown\nthat a higher-order component has a smaller contribution. With the increase of\ndeformation, the high-order components get larger, while at the same\ndeformation, the high-order components of a heavy nucleus play a more important\nrole than that of a light one.", "category": "nucl-th" }, { "text": "Coupled-channel continuum eigenchannel basis: The goal of this paper is to calculate bound, resonant and scattering states\nin the coupled-channel formalism without relying on the boundary conditions at\nlarge distances. The coupled-channel solution is expanded in eigenchannel bases\ni.e. in eigenfunctions of diagonal Hamiltonians. Each eigenchannel basis may\ninclude discrete and discretized continuum (real or complex energy) single\nparticle states. The coupled-channel solutions are computed through\ndiagonalization in these bases. The method is applied to a few two-channels\nproblems. The exact bound spectrum of the Poeschl-Teller potential is well\ndescribed by using a basis of real energy continuum states. For deuteron\ndescribed by Reid potential, the experimental energy and the S and D contents\nof the wave function are reproduced in the asymptotic limit of the cutoff\nenergy. For the Noro-Taylor potential resonant state energy is well reproduced\nby using the complex energy Berggren basis. It is found that the expansion of\nthe coupled-channel wave function in these eigenchannel bases require less\ncomputational efforts than the use of any other basis. The solutions are stable\nand converge as the cutoff energy increases.", "category": "nucl-th" }, { "text": "Description of resonant states in the shell model: A technique for describing scattering states within the nuclear shell model\nis proposed. This technique is applied to scattering of nucleons by $\\alpha$\nparticles based on ab initio No-Core Shell Model calculations of $^5$He and\n$^5$Li nuclei with JISP16 NN interaction.", "category": "nucl-th" }, { "text": "Trees and Islands -- Machine learning approach to nuclear physics: We implement machine learning algorithms to nuclear data. These algorithms\nare purely data driven and generate models that are capable to capture\nintricate trends. Gradient boosted trees algorithm is employed to generate a\ntrained model from existing nuclear data, which is used for prediction for data\nof damping parameter, shell correction energies, quadrupole deformation,\npairing gaps, level densities and giant dipole resonance for large number of\nnuclei. We, in particular, predict level density parameter for superheavy\nelements which is of great current interest. The predictions made by the\nmachine learning algorithm is found to have standard deviation from 0.00035 to\n0.73.", "category": "nucl-th" }, { "text": "Scaling behavior at high p_T and the p/pi ratio: We first show that the pions produced at high $p_T$ in heavy-ion collisions\nover a wide range of high energies exhibit a scaling behavior when the\ndistributions are plotted in terms of a scaling variable. We then use the\nrecombination model to calculate the scaling quark distribution just before\nhadronization. From the quark distribution it is then possible to calculate the\nproton distribution at high $p_T$, also in the framework of the recombination\nmodel. The resultant $p/\\pi$ ratio exceeds one in the intermediate $p_T$ region\nwhere data exist, but the scaling result for the proton distribution is not\nreliable unless $p_T$ is high enough to be insensitive to the scale-breaking\nmass effects.", "category": "nucl-th" }, { "text": "Combining phase-space and time-dependent reduced density matrix approach\n to describe the dynamics of interacting fermions: The possibility to apply phase-space methods to many-body interacting systems\nmight provide accurate descriptions of correlations with a reduced numerical\ncost. For instance, the so--called stochastic mean-field phase-space approach,\nwhere the complex dynamics of interacting fermions is replaced by a statistical\naverage of mean-field like trajectories is able to grasp some correlations\nbeyond the mean-field. We explore the possibility to use alternative equations\nof motion in the phase-space approach. Guided by the BBGKY hierarchy, equations\nof motion that already incorporate part of the correlations beyond mean-field\nare employed along each trajectory. The method is called Hybrid Phase-Space\n(HPS) because it mixes phase-space techniques and the time-dependent reduced\ndensity matrix approach. The novel approach is applied to the one-dimensional\nFermi-Hubbard model. We show that the predictive power is improved compared to\nthe original stochastic mean-field method. In particular, in the weak-coupling\nregime, the results of the HPS theory can hardly be distinguished from the\nexact solution even for long time.", "category": "nucl-th" }, { "text": "$\u03b3^\\ast \u03b3\\to \u03b7, \u03b7^\\prime$ transition form factors: Using a continuum approach to the hadron bound-state problem, we calculate\n$\\gamma^\\ast \\gamma \\to \\eta, \\eta^\\prime$ transition form factors on the\nentire domain of spacelike momenta, for comparison with existing experiments\nand in anticipation of new precision data from next-generation $e^+ e^-$\ncolliders. One novel feature is a model for the contribution to the\nBethe-Salpeter kernel deriving from the non-Abelian anomaly, an element which\nis crucial for any computation of $\\eta, \\eta^\\prime$ properties. The study\nalso delivers predictions for the amplitudes that describe the light- and\nstrange-quark distributions within the $\\eta, \\eta^\\prime$. Our results compare\nfavourably with available data. Important to this at large-$Q^2$ is a sound\nunderstanding of QCD evolution, which has a visible impact on the $\\eta^\\prime$\nin particular. Our analysis also provides some insights into the properties of\n$\\eta, \\eta^\\prime$ mesons and associated observable manifestations of the\nnon-Abelian anomaly.", "category": "nucl-th" }, { "text": "A new single-particle basis for nuclear many-body calculations: Predominantly, harmonic oscillator single-particle wave functions are the\nchoice as a basis in ab-initio nuclear many-body calculations. These\nwave-functions, although very convenient in order to evaluate the matrix\nelements of the interaction in the laboratory frame, have a too fast fall-off\nat large distances. In the past, in alternative to the harmonic oscillator,\nother single-particle wave functions have been proposed. In this work we\npropose a new single-particle basis, directly linked to the nucleon-nucleon\ninteraction. This new basis is orthonormal and complete, has the proper\nasymptotic behavior at large distances and does not contain the continuum which\nwould pose severe convergence problems in nuclear many body calculations. We\nconsider the newly proposed NNLO-opt nucleon-nucleon interaction, without any\nrenormalization.\n We show that unlike other basis, this single-particle representation has a\ncomputational cost similar to the harmonic oscillator basis with the same space\ntruncation and it gives lower energies for ${}^6He$ and ${}^6Li$.", "category": "nucl-th" }, { "text": "O(12) limit and complete classification of symmetry schemes in\n proton-neutron interacting boson model: It is shown that the proton-neutron interacting boson model (pnIBM) admits\nnew symmetry limits with O(12) algebra which break F-spin but preserves the\nquantum number M_F. The generators of O(12) are derived and the quantum number\n`v' of O(12) for a given boson number N is determined by identifying the\ncorresponding quasi-spin algebra. The O(12) algebra generates two symmetry\nschemes and for both of them, complete classification of the basis states and\ntypical spectra are given. With the O(12) algebra identified, complete\nclassification of pnIBM symmetry limits with good M_F is established.", "category": "nucl-th" }, { "text": "Growth of Interaction Between Antiprotons (Negative Hyperons) and Nuclei\n in Polarized Matter: The Possibility to Study the Spin-Dependent Part of the\n Forward Scattering Amplitude in the Range of Low-Energies: The influence of Coulomb interaction on the phenomenon of \"optical\" spin\nrotation of negatively charged particles (antiprotons, etc.) moving in matter\nwith polarized nuclei is considered. It is shown that because the density of\nthe antiproton (negative hyperon) wave function on the nucleus increases, the\nspin precession frequency grows as the particle decelerates. As a result, spin\nrotation of negatively charged particles becomes observable despite their rapid\ndeceleration. This provides information about the spin--dependent part of the\namplitude of coherent elastic zero--angle scattering in the range of low\nenergies, where scattering experiments are practically impossible to perform.", "category": "nucl-th" }, { "text": "Thermal and transport properties in central heavy-ion reactions around a\n few hundred MeV/nucleon: Thermalization process of nuclear matter in central fireball region of\nheavy-ion collisions is investigated by employing an extension model of\nBoltzmann-Uehling-Uhlenbeck, namely the Van der Waals\nBoltzmann-Uehling-Uhlenbeck (VdWBUU) model. Temperature ($T$) is extracted by\nthe quantum Fermion fluctuation approach and other thermodynamic quantities,\nsuch as density ($\\rho$), entropy density ($s$), shear viscosity ($\\eta$),\nisospin diffusivity ($D_{I}$) and heat conductivity ($\\kappa$), are also\ndeduced. The liquid-like and gas-like phase signs are discussed through the\nbehavior of shear viscosity during heavy-ion collisions process with the VdWBUU\nmodel.", "category": "nucl-th" }, { "text": "Symmetry Energy I: Semi-Infinite Matter: Energy for a nucleus is considered in macroscopic limit, in terms of nucleon\nnumbers. Further considered for a nuclear system is the Hohenberg-Kohn energy\nfunctional, in terms of proton and neutron densities. Finally,\nSkyrme-Hartree-Fock calculations are carried out for a half-infinite\nparticle-stable nuclear-matter. In each case, the attention is focused on the\nrole of neutron-proton asymmetry and on the nuclear symmetry energy. We extend\nthe considerations on the symmetry term from an energy formula to the\nrespective term in the Hohenberg-Kohn functional. We show, in particular, that\nin the limit of an analytic functional, and subject to possible Coulomb\ncorrections, it is possible to construct isoscalar and isovector densities out\nof the proton and neutron densities, that retain a universal relation to each\nother, approximately independent of asymmetry. In the so-called local\napproximation, the isovector density is inversely proportional to the symmetry\nenergy in uniform matter at the local isoscalar density. Generalized symmetry\ncoefficient of a nuclear system is related, in the analytic limit of a\nfunctional, to an integral of the isovector density. We test the relations,\ninferred from the Hohenberg-Kohn functional, in the Skyrme-Hartree-Fock\ncalculations of half-infinite matter. Within the calculations, we obtain\nsurface symmetry coefficients and parameters characterizing the densities, for\nthe majority of Skyrme parameterizations proposed in the literature. The\nvolume-to-surface symmetry-coefficient ratio and the displacement of nuclear\nisovector relative to isoscalar surfaces both strongly increase as the slope of\nsymmetry energy in the vicinity of normal density increases.", "category": "nucl-th" }, { "text": "The effect of early chemical freeze out on radial and elliptic flow from\n a full 3D hydrodynamic model: We investigate the effect of early chemical freeze-out on radial and elliptic\nflow by using a fully three dimensional hydrodynamic model. We find that the\ntime evolution of temperature and the thermal freeze-out temperature dependence\nof average radial flow are different from the results by using a conventional\nhydrodynamic model in which chemical equilibrium is always assumed. We also\nanalyse the p_t spectrum and v_2(p_t) at the RHIC energy and consistently\nreproduce experimental data by choosing the thermal freeze-out temperature T_th\n= 140 MeV.", "category": "nucl-th" }, { "text": "Thermal conductivity in dynamics of first-order phase transition: Effects of thermal conductivity on the dynamics of first-order phase\ntransitions are studied. Important consequences of a difference of the\nisothermal and adiabatic spinodal regions are discussed. We demonstrate that in\nhydrodynamical calculations at non-zero thermal conductivity, $\\kappa \\neq 0$,\nonset of the spinodal instability occurs, when the system trajectory crosses\nthe isothermal spinodal line. Only for $\\kappa = 0$ it occurs at a cross of the\nadiabatic spinodal line. Therefore ideal hydrodynamics is not suited for an\nappropriate description of first-order phase transitions.", "category": "nucl-th" }, { "text": "Faddeev-Yakubovsky search for Lambda-Lambda hydrogen-4: Evidence for particle stability of Lambda-Lambda hydrogen-4 (4LLH) has been\nsuggested by the BNL-AGS E906 experiment. We report on Faddeev-Yakubovsky\ncalculations for the four-body Lambda-Lambda-p-n system using Lambda-N\ninteractions which reproduce the observed binding energy of Lambda hydrogen-3\n(3LH) within a Faddeev calculation for the Lambda-p-n subsystem. No 4LLH bound\nstate is found over a wide range of Lambda-Lambda interaction strengths,\nalthough the Faddeev equations for a three-body Lambda-Lambda-d model of 4LLH\nadmit a 1+ bound state for as weak a Lambda-Lambda interaction strength as\nrequired to reproduce the binding energy of Lambda-Lambda Helium-6 (6LLHe).", "category": "nucl-th" }, { "text": "Coupling of pairing and triaxial shape vibrations in collective states\n of $\u03b3$-soft nuclei: In addition to shape oscillations, low-energy excitation spectra of deformed\nnuclei are also influenced by pairing vibrations. The simultaneous description\nof these collective modes and their coupling has been a long-standing problem\nin nuclear structure theory. Here we address the problem in terms of\nself-consistent mean-field calculations of collective deformation energy\nsurfaces, and the framework of the interacting boson approximation. In addition\nto quadrupole shape vibrations and rotations, the explicit coupling to pairing\nvibrations is taken into account by a boson-number non-conserving Hamiltonian,\nspecified by a choice of a universal density functional and pairing\ninteraction. An illustrative calculation for $^{128}$Xe and $^{130}$Xe shows\nthe importance of dynamical pairing degrees of freedom, especially for\nstructures built on low-energy $0^+$ excited states, in $\\gamma$-soft and\ntriaxial nuclei.", "category": "nucl-th" }, { "text": "Elastic and dynamic form factors of an atomic nucleus in the shell model\n with correction for the center-of-mass motion: Analytical expressions for the elastic and dynamic form factors (FFs) are\nderived in the shell model (SM) with a potential well of finite depth. The\nconsideration takes into account the motion of the target-nucleus center of\nmass (CM). Explanation is suggested for a simultaneous shrinking of the density\nand momentum distributions of nucleons in nuclei. The convenient working\nformulae are given to handle the expectation values of relevant multiplicative\noperators in case of the 1s-1p shell nuclei.", "category": "nucl-th" }, { "text": "Nuclear Responses to Electro-Weak Probes and In-Medium Chiral\n Perturbation Theory: We discuss two topics concerning the application of chiral perturbation\ntheory to nuclear physics: (1) the latest developments in the study of possible\nkaon condensation in dense baryonic systems; (2) nuclear responses to\nelectro-weak probes.", "category": "nucl-th" }, { "text": "Microscopic predictions for production of neutron rich nuclei in the\n reaction $^\\mathbf{176}\\mathbf{Yb}+{}^\\mathbf{176}\\mathbf{Yb}$: Background: Production of neutron-rich nuclei is of vital importance to both\nunderstanding nuclear structure far from stability and to informing\nastrophysical models of the rapid neutron capture process (r-process).\nMultinucleon transfer (MNT) in heavy-ion collisions offers a possibility to\nproduce neutron-rich nuclei far from stability.\n Purpose: The $^{176}\\mathrm{Yb}+{}^{176}\\mathrm{Yb}$ reaction has been\nsuggested as a potential candidate to explore the neutron-rich region\nsurrounding the principal fragments. The current study has been conducted with\nthe goal of providing guidance for future experiments wishing to study this (or\nsimilar) system.\n Methods: Time-dependent Hartree-Fock (TDHF) and its time-dependent\nrandom-phase approximation (TDRPA) extension are used to examine both\nscattering and MNT characteristics in $^{176}\\mathrm{Yb}+{}^{176}\\mathrm{Yb}$.\nTDRPA calculations are performed to compute fluctuations and correlations of\nthe neutron and proton numbers, allowing for estimates of primary fragment\nproduction probabilities.\n Results: Both scattering results from TDHF and transfer results from the\nTDRPA are presented for different energies, orientations, and impact\nparameters. In addition to fragment composition, scattering angles and total\nkinetic energies, as well as correlations between these observables are\npresented.\n Conclusions: $^{176}\\mathrm{Yb}+{}^{176}\\mathrm{Yb}$ appears to be an\ninteresting probe for the mid-mass neutron-rich region of the chart of\nnuclides. The predictions of both TDHF and TDRPA are speculative, and will\nbenefit from future experimental results to test the validity of this approach\nto studying MNT in heavy, symmetric collisions.", "category": "nucl-th" }, { "text": "Transport study of charged current interactions in neutrino-nucleus\n reactions: Within a dynamical transport approach we investigate charged current\ninteractions in neutrino-nucleus reactions for neutrino energies of 0.3 - 1.5\nGeV with particular emphasis on resonant pion production channels via the\n$\\Delta_{33}(1232)$ resonance. The final-state-interactions of the resonance as\nwell as of the emitted pions are calculated explicitly for $^{12}C$ and\n$^{56}Fe$ nuclei and show a dominance of pion suppression at moderate momenta\n$p_\\pi >$ 0.2 GeV/c. A comparison to integrated $\\pi^+$ spectra for $\\nu_\\mu +\n^{12}C$ reactions with the available (preliminary) data demonstrates a\nreasonable agreement.", "category": "nucl-th" }, { "text": "Odd-Even Staggering of Nuclear Masses: Pairing or Shape Effect?: The odd-even staggering of nuclear masses was recognized in the early days of\nnuclear physics. Recently, a similar effect was discovered in other finite\nfermion systems, such as ultrasmall metallic grains and metal clusters. It is\nbelieved that the staggering in nuclei and grains is primarily due to pairing\ncorrelations (superconductivity), while in clusters it is caused by the\nJahn-Teller effect. We find that, for light and medium-mass nuclei, the\nstaggering has two components. The first one originates from pairing while the\nsecond, comparable in magnitude, has its roots in the deformed mean field.", "category": "nucl-th" }, { "text": "Towards a new quark-nuclear matter EoS for applications in astrophysics\n and heavy-ion collisions: The aim of our work is to develop a unified equation of state (EoS) for\nnuclear and quark matter for a wide range in temperature, density and isospin\nso that it becomes applicable for heavy-ion collisions as well as for the\nastrophysics of neutron stars, their mergers and supernova explosions. As a\nfirst step, we use improved EoS for the hadronic and quark matter phases and\njoin them via Maxwell construction. We discuss the limitations of a 2-phase\ndescription and outline steps beyond it, towards the formulation of a unified\nquark-nuclear matter EoS on a more fundamental level by a cluster virial\nexpansion.", "category": "nucl-th" }, { "text": "A Schematic Model for $\u03c1$-$a_1$ Mixing at Finite Density and\n In-Medium Effective Lagrangian: Based on schematic two-level models extended to $a_1$-meson degrees of\nfreedom, we investigate possible mechanisms of chiral restoration in the\nvector/axialvector channels in cold nuclear matter. In the first part of this\narticle we employ the massive Yang-Mills framework to construct an effective\nchiral Lagrangian based on low-energy mesonic modes at finite density. The\nlatter are identified through nuclear collective excitations of `meson'-sobar\ntype such as $\\pi\\leftrightarrow [\\Delta (1232)N^{-1}]\\equiv\\hat\\pi$,\n$\\rho\\leftrightarrow [N^* (1520)N^{-1}]\\equiv\\hat\\rho$, etc.. In a mean-field\ntype treatment the in-medium gauge coupling $\\hat g$, the (axial-) vector meson\nmasses and $\\hat f_\\pi$ are found to decrease with density indicating the\napproach towards chiral restoration in the language of in-medium effective\nfields. In the second part of our analysis we evaluate the (first) in-medium\nWeinberg sum rule which relates vector and axialvector correlators to the pion\ndecay constant. Using in-medium $\\rho$/$a_1$ spectral functions (computed in\nthe two-level model) also leads to a substantial reduction of the pion decay\nconstant with increasing density.", "category": "nucl-th" }, { "text": "Exact solution of equations for proton localization in neutron star\n matter: The rigorous treatment of proton localization phenomenon in asymmetric\nnuclear matter is presented. The solution of proton wave function and neutron\nbackground distribution is found by the use of the extended Thomas-Fermi\napproach. The minimum of energy is obtained in the Wigner- Seitz approximation\nof spherically symmetric cell. The analysis of three different nuclear models\nsuggests that the proton localization is likely to take place in the interior\nof neutron star.", "category": "nucl-th" }, { "text": "Phenomenological QCD equations of state for neutron star mergers: Thermal QCD equations of state at high baryon density are sensitive to the\nphase structure and the resulting excitation modes. The leading contribution at\nlow temperature can be either ~p_F^2 T^2 (pF: Fermi momentum, T: temperature)\nfor phases with gapless quarks, or ~T^4 for phases with gapped quarks. In the\nlatter the thermal pressure is dominated by collective modes. Starting with a\nschematic quark model developed for neutron star structure, we estimate the\nthermal contributions and zero point energy from the Nambu-Goldstone modes by\nbuilding them upon the mean field background for the color-flavor-locked quark\nmatter. Applying the phase shift representation for thermodynamic potentials,\nwe include not only the bound state pairs but also resonating pairs. According\nto the Levinson's theorem, the high energy contributions tend to cancel the\npole contributions to the thermodynamics, tempering the UV behaviors in the\nzero point energy. Our primary target in this talk is the domain with baryon\ndensity nB as large as ~ 5-10n_0 (n_0 = 0.16 fm^{-3}: nuclear saturation\ndensity), and the temperature T of the order ~30-100 MeV. The insights into\nthis domain may be obtained through the future detection of gravitational waves\nfrom neutron star merging events.", "category": "nucl-th" }, { "text": "Transverse mass scaling of dilepton radiation off a quark-gluon plasma: The spectrum of dileptons produced by the quark-gluon plasma in an\nultrarelativistic nucleus-nucleus collision depends only, to a good\napproximation, on the transverse mass M_t of the dilepton. This scaling is\nexact as long as transverse flow is negligible, and the system is in local\nthermal equilibrium. We implement a state-of-the-art modelization of kinetic\nand chemical equilibration in the early stages of the evolution to study the\nmodifications of the spectrum. Violations of M_t scaling resulting from these\neffects are evaluated as a function of the shear viscosity to entropy ratio\n(eta/s) that controls the equilibration time. We determine the dependence of\nthe spectrum on system size, centrality, rapidity, and collision energy. We\nshow that the quark-gluon plasma produces more dileptons than the Drell-Yan\nprocess up to invariant masses of order M = 4 GeV. Due to different kinematics,\nfor a given M_t , the dependence of the dilepton yield on M is opposite for the\ntwo processes, so that experiment alone can in principle determine which\nprocess dominates.", "category": "nucl-th" }, { "text": "An improvement on RPA based on a Boson mapping: We use a solvable model to perform modified dyson mapping and reveal the\nunphysical-state effects in the original Random Phase Approximation (RPA). We\nthen propose a method to introduce the RPA and improve it based on a Boson\nmapping.", "category": "nucl-th" }, { "text": "Analysis of NN Amplitudes up to 2.5 GeV: An Optical Model and Geometric\n Interpretation: We analyse the SM97 partial wave amplitudes for nucleon--nucleon (NN)\nscattering to 2.5 GeV, in which resonance and meson production effects are\nevident for energies above pion production threshold. Our analyses are based\nupon boson exchange or quantum inversion potentials with which the\nsub-threshold data are fit perfectly. Above 300 MeV they are extrapolations, to\nwhich complex short ranged Gaussian potentials are added in the spirit of the\noptical models of nuclear physics and of diffraction models of high energy\nphysics. The data to 2.5 GeV are all well fit. The energy dependences of these\nGaussians are very smooth save for precise effects caused by the known $\\Delta$\nand N$^\\star$ resonances. With this approach, we confirm that the geometrical\nimplications of the profile function found from diffraction scattering are\npertinent in the regime 300 MeV to 2.5 GeV and that the overwhelming part of\nmeson production comes from the QCD sector of the nucleons when they have a\nseparation of their centres of 1 to 1.2 fm. This analysis shows that the\nelastic NN scattering data above 300 MeV can be understood with a local\npotential operator as well as has the data below 300 MeV.", "category": "nucl-th" }, { "text": "Gross features of finite nuclei at finite temperatures: A simple expression is obtained for the low temperature behavior of the\nenergy and entropy of finite nuclei for $20\\leq A\\leq 250$. The dependence on\n$A$ of these quantities is for the most part due to the presence of the\nasymmetry energy.", "category": "nucl-th" }, { "text": "Isospin-asymmetric nuclear matter: This study uses classical molecular dynamics to simulate infinite nuclear\nmatter and study the effect of isospin asymmetry on bulk properties such as\nenergy per nucleon, pressure, saturation density, compressibility and symmetry\nenergy. The simulations are performed on systems embedded in periodic boundary\nconditions with densities and temperatures in the ranges $\\rho$=0.02 to 0.2\nfm$^{-3}$ and T = 1, 2, 3, 4 and 5 MeV, and with isospin content of\n$x=Z/A$=0.3, 0.4 and 0.5. The results indicate that symmetric and asymmetric\nmatter are self-bound at some temperatures and exhibit phase transitions from a\nliquid phase to a liquid-gas mixture. The main effect of isospin asymmetry is\nfound to be a reduction of the equilibrium densities, a softening of the\ncompressibility and a disappearance of the liquid-gas phase transition. A\nprocedure leading to the evaluation of the symmetry energy and its variation\nwith the temperature was devised, implemented and compared to mean field theory\nresults.", "category": "nucl-th" }, { "text": "An exact solution of spherical mean-field plus orbit-dependent\n non-separable pairing model with two non-degenerate j-orbits: An exact solution of nuclear spherical mean-field plus orbit-dependent\nnon-separable pairing model with two non-degenerate j-orbits is presented. The\nextended one-variable Heine-Stieltjes polynomials associated to the Bethe\nansatz equations of the solution are determined, of which the sets of the zeros\ngive the solution of the model, and can be determined relatively easily. A\ncomparison of the solution to that of the standard pairing interaction with\nconstant interaction strength among pairs in any orbit is made. It is shown\nthat the overlaps of eigenstates of the model with those of the standard\npairing model are always large, especially for the ground and the first excited\nstate. However, the quantum phase crossover in the non-separable pairing model\ncannot be accounted for by the standard pairing interaction.", "category": "nucl-th" }, { "text": "Inhomogeneous freeze-out in heavy-ion collisions: Relative hadron abundances from high-energy heavy-ion collisions reveal\nsubstantial inhomogeneities of temperature and baryon-chemical potential within\nthe decoupling volume. The freeze-out volume is not perfectly \"stirred\", i.e.\nthe concentrations of pions, kaons, (anti-) nucleons etc are inhomogeneous.\nSuch inhomogeneities in the late stages of the hydrodynamic expansion might be\ntraces of a first-order phase transition.", "category": "nucl-th" }, { "text": "Color Decoherence in In-Medium QCD Cascades: The talk, based on \\cite{LN10}, analyzes the consequences of the assumption\nthat the effects of quantum coherence and the resulting angular ordering in QCD\ncascades are disrupted within the hot fireball created in ultrarelativistic\nheavy ion collisions.", "category": "nucl-th" }, { "text": "Relation between the density-matrix theory and the pairing theory: The time-dependent density-matrix theory (TDDM) gives a correlated ground\nstate as a stationary solution of the time-dependent equations for one-body and\ntwo-body density matrices. The small amplitude limit of TDDM (STDDM) is a\nversion of extended RPA theories which include the effects of ground state\ncorrelations. It is shown that the solutions of the Hartree-Fock Bogoliubov\ntheory and the quasi-particle RPA satisfy the TDDM and STDDM equations,\nrespectively, when only pairing-type correlations are taken into account in\nTDDM and STDDM.", "category": "nucl-th" }, { "text": "Microcanonical studies on isoscaling: The exponential scaling of isotopic yields is investigated for sources of\ndifferent sizes over a broad range of excitation energies and freeze-out\nvolumes, in both primary and asymptotic stages of the decay in the framework of\na microcanonical multifragmentation model. It was found that the scaling\nparameters have a strong dependence on the considered pair of equilibrated\nsources and excitation energy and are affected by the secondary particle\nemission of the break-up fragments. No significant influence of the freeze-out\nvolume on the considered isotopic ratios has been observed. Deviations of\nmicrocanonical results from grandcanonical expectations are discussed.", "category": "nucl-th" }, { "text": "State-of-the-art of beyond mean field theories with nuclear density\n functionals: We present an overview of beyond mean field theories (BMFT) based on the\ngenerator coordinate method (GCM) and the recovery of symmetries used in\nnuclear physics with effective forces. After a reminder of the\nHartree-Fock-Bogoliubov (HFB) theory a discussion of the shortcomings of any\nmean field approximation (MFA) is presented. The recovery of the symmetries\nspontaneously broken in the HFB approach, in particular the angular momentum,\nis necessary, among others, to describe excited states and transitions.\nParticle number projection is needed to guarantee the right number of protons\nand neutrons. Furthermore a projection before the variation prevents the\npairing collapse in the weak pairing regime. The lack of fluctuations around\nthe average values of the MFA is a shortcoming of this approach. To build in\ncorrelations in BMFT one selects the relevant degrees of freedom: quadrupole,\noctupole and the pairing vibrations as well as the single particle ones. In the\nGCM the operators representing these degrees of freedom are used as coordinates\nto generate a collective subspace. The highly correlated GCM wave function is\nfinally written as a linear combination of a projected basis of this space. The\nvariation of the coefficients of the linear combination leads to the\nHill-Wheeler equation. We discuss the classical beta and gamma vibrations by\nconsidering the quadrupole operators as coordinates. We present pairing\nfluctuations by considering the pairing gaps as generator coordinates. Lastly\nthe explicit consideration of the time reversal symmetry breaking in the HFB\nwave function by the cranking procedure allows the alignment of nucleon pairs\nopening a new dimension in the BMFT calculations. Abundant calculations with\nthe Gogny force illustrate the state-of-the-art of BMFTs with density\nfunctionals. We conclude with a thorough discussion on the potential poles of\nthe theory.", "category": "nucl-th" }, { "text": "Antisymmetrization in the Multicluster Dynamic Model of Nuclei and the\n Nucleon Exchange Effects: A modified version of the Multicluster Dynamic Model of nuclei is proposed to\nconstruct completely antisymmetrized wave functions of multicluster systems. An\noverlap kernel operator is introduced to renormalize the total wave function\nafter antisymmetrization between nucleons in different clusters. A\ngroup-theoretical method is developed to analyze the role of the exchange\neffects arising in the calculation of the various observables of multicluster\nsystems due to this antisymmetrization.\n The Antisymmetrized version of the Multicluster Dynamic Model is applied to\nthe six-nucleon systems treating them as alpha-2N ones.The static and dynamic\ncharacteristics of the six-nucleon systems manifested in electron and pi-meson\nscattering, muon capture, beta-decay, pion photoproduction, etc., are\ncalculated.", "category": "nucl-th" }, { "text": "Is Anomalous Production of Omega and anti-Omega Evidence for Disoriented\n Chiral Condensates?: No conventional picture of nucleus-nucleus collisions has yet been able to\nexplain the abundance of Omega and anti-Omega hyperons in central collisions\nbetween Pb nuclei at 158 A GeV at the CERN SPS. We argue that this is evidence\nthat they are produced as topological defects arising from the formation of\ndisoriented chiral condensates (DCC) with an average domain size of about 2 fm.", "category": "nucl-th" }, { "text": "Dynamical evolution of critical fluctuations and its observation in\n heavy ion collisions: We study time evolution of critical fluctuations of conserved charges near\nthe QCD critical point in the context of relativistic heavy ion collisions. A\nstochastic diffusion equation is employed in order to describe the diffusion\nproperty of the critical fluctuation arising from the coupling of the order\nparameter field to conserved charges. We show that the diffusion property gives\nrise to a possibility of probing the early time fluctuations through the\nrapidity window dependence of the second-order cumulant and correlation\nfunction of conserved charges. It is pointed out that their non-monotonic\nbehaviors as functions of the rapidity interval are robust experimental signals\nfor the existence of the critical enhancement around the QCD critical point.", "category": "nucl-th" }, { "text": "Multiple chiral doublet candidate nucleus $^{105}$Rh in a relativistic\n mean-field approach: Following the reports of two pairs of chiral doublet bands observed in\n$^{105}$Rh, the adiabatic and configuration-fixed constrained triaxial\nrelativistic mean-field (RMF) calculations are performed to investigate their\ntriaxial deformations with the corresponding configuration and the possible\nmultiple chiral doublet (M$\\chi$D) phenomenon. The existence of M$\\chi$D\nphenomenon in $^{105}$Rh is highly expected.", "category": "nucl-th" }, { "text": "Origin of the mass splitting of elliptic anisotropy in a multiphase\n transport model: The mass splitting of elliptic anisotropy ($v_2$) at low transverse momentum\nis considered as a hallmark of hydrodynamic collective flow. We investigate a\nmultiphase transport (AMPT) model where the $v_2$ is mainly generated by an\nanisotropic escape mechanism, not of the hydrodynamic flow nature, and where\nmass splitting is also observed. We demonstrate that the $v_2$ mass splitting\nin AMPT is small right after hadronization (especially when resonance decays\nare included); the mass splitting mainly comes from hadronic rescatterings,\neven though their contribution to the overall charged hadron $v_2$ is small.\nThese findings are qualitatively the same as those from hybrid models that\ncombine hydrodynamics with a hadron cascade. We further show that there is no\nqualitative difference between heavy ion collisions and small system\ncollisions. Our results indicate that the $v_2$ mass splitting is not a unique\nsignature of hydrodynamic collective flow and thus cannot distinguish whether\nthe elliptic flow is generated mainly from hydrodynamics or the anisotropic\nparton escape.", "category": "nucl-th" }, { "text": "Separable potential model for $K^{-}N$ interactions at low energies: The effective separable meson-baryon potentials are constructed to match the\nequivalent chiral amplitudes up to the second order in external meson momenta.\nWe fit the model parameters (low energy constants) to the threshold and low\nenergy $K^{-}p$ data. In the process, the $K^{-}$-proton bound state problem is\nsolved exactly in the momentum space and the 1s level characteristics of the\nkaonic hydrogen are computed simultaneously with the available low energy\n$K^{-}p$ cross sections. The model is also used to describe the $\\pi \\Sigma$\nmass spectrum and the energy dependence of the $K^{-}n$ amplitude.", "category": "nucl-th" }, { "text": "Pions in magnetic field at finite temperature: Pions in external magnetic field are investigated in the frame of a\nPauli-Villars regularized Nambu--Jona-Lasinio model. The meson propagators in\nterms of quark bubbles in Ritus and Schwinger schemes are analytically derived,\nand pion masses are numerically calculated in the Ritus scheme. For neutral and\ncharged pions at finite temperature, there exist respectively one and three\nmass jumps at the corresponding Mott transition points, due to the discrete\nenergy levels of the two constituent quarks in magnetic field.", "category": "nucl-th" }, { "text": "Systematic study of proton radioactivity half-lives based on the\n relationship between the Skyrme-Hartree-Fock and the macroscopic quantities\n of nuclear matter: In the present work, we systematically study the proton radioactivity\nhalf-lives of 33 spherical nuclei based on the relationship between the Skyrme\nparameters and the macroscopic quantities of nuclear matter. Using the\ntwo-potential approach with the spherical Skyrme-Hartree-Fock model, the\ncorrelation between proton radioactivity half-life and macroscopic quantities\nwas analyzed. Moreover, we obtained a new Skyrme parameter set by fitting the\ntwo most weighted macroscopic quantities. Compared with Skyrme parameters MSL0\nand the theoretical model of proton radioactivity UDLP, the theoretical proton\nradioactivity half-life calculated by the new Skyrme parameter set can better\nreproduce the experimental data.", "category": "nucl-th" }, { "text": "Fusion dynamics of symmetric systems near barrier energies: The enhancement of the sub-barrier fusion cross sections was explained as the\nlowering of the dynamical fusion barriers within the framework of the improved\nisospin-dependent quantum molecular dynamics (ImIQMD) model. The numbers of\nnucleon transfer in the neck region are appreciably dependent on the incident\nenergies, but strongly on the reaction systems. A comparison of the neck\ndynamics is performed for the symmetric reactions $^{58}$Ni+$^{58}$Ni and\n$^{64}$Ni+$^{64}$Ni at energies in the vicinity of the Coulomb barrier. An\nincrease of the ratios of neutron to proton in the neck region at initial\ncollision stage is observed and obvious for neutron-rich systems, which can\nreduce the interaction potential of two colliding nuclei. The distribution of\nthe dynamical fusion barriers and the fusion excitation functions are\ncalculated and compared them with the available experimental data.", "category": "nucl-th" }, { "text": "Systematics of semi-microscopic proton-nucleus optical potential at low\n energies relevant to nuclear astrophysics: Astrophysical models studying the origin of the p-nuclei require knowledge of\nthe reaction rates of photodisintegrations and capture reactions. Since\nexperimental data at astrophysically relevant energies are limited, reaction\nrate calculations rely on Hauser-Feshbach (HF) theory predictions. The HF\ntheory requires nuclear physics input such as masses, level densities,\n$\\gamma$-ray strength functions and proton-nucleus optical potentials (pOMP).\nThe scope of this work is to improve a global semi-microscopic pOMP at energies\nrelevant to the p-process. This is achieved by adjusting the normalization\nparameters of the OMP to all available proton-capture cross sections measured\nat low energies. By establishing the systematic behaviour of these parameters,\none expects to enhance the predictive power of the pOMP when expanding to mass\nregions where no data exists. The HF calculations were obtained using TALYS\ncode. The normalization parameters for the real and imaginary central\npotentials ($\\lambda_V$ and $\\lambda_W$) were adjusted to fit the proton data\nin the energy range where the cross-section are independent of the other\nnuclear inputs. Results show that the $\\lambda_V$ parameter has a strong mass\ndependence that can be described by a second-degree polynomial function for A\n$\\leq$ 100 and an exponential increase for 100 < A < 162. Though variations of\nthe $\\lambda_W$ have a smaller effect on the calculations, a global increase by\n50$\\%$ improves the results for certain nuclei without affecting the rest of\nthe cases. The resulting adjustment functions were obtained by fitting all\nsuitable proton data and can be used with reasonable confidence to generate the\nglobal semi-microscopic pOMP for nuclei in the medium to heavy mass region. For\nbetter statistics, more low-energy (p,$\\gamma$) cross section data are needed\nfor heavier nuclei with mass A $>$ 100.", "category": "nucl-th" }, { "text": "Event-by-event $v_n$ correlations of soft hadrons and heavy mesons in\n heavy ion collisions: In this paper heavy quark energy loss models are embedded in full\nevent-by-event viscous hydrodynamic simulations to investigate the nuclear\nsuppression factor and azimuthal anisotropy of D$^0$ mesons in PbPb collisions\nat 5.02 TeV in the $p_T$ range 8-40 GeV. In our model calculations, the\n$R_\\text{AA}$ of D$^0$ mesons is consistent with experimental data from the CMS\nexperiment. We present the first calculations of heavy flavor cumulants\n$v_2\\{2\\}$ and $v_3\\{2\\}$ (and also discuss $v_2\\{4\\}$), which is also\nconsistent with experimental data. Event-shape engineering techniques are used\nto compute the event-by-event correlation between the soft hadron $v_n$ and the\nheavy meson $v_n$. We predict a linear correlation between these observables on\nan event-by-event basis.", "category": "nucl-th" }, { "text": "Two-scale scalar mesons in nuclei: We generalize the linear sigma model in order to develop a chiral-invariant\nmodel of nuclear structure. The model is natural, and contains not only the\nusual sigma meson which is the chiral partner of the pion but also a new\nchiral-singlet that is responsible for the medium-range nucleon-nucleon\nattraction. This approach provides significant advantages in terms of its\ndescription of nuclear matter and finite nuclei in comparison with conventional\nmodels based on the linear sigma model.", "category": "nucl-th" }, { "text": "Low Energy Theorems For Nucleon-Nucleon Scattering: Low energy theorems are derived for the coefficients of the effective range\nexpansion in s-wave nucleon-nucleon scattering valid to leading order in an\nexpansion in which both $m_\\pi$ and $1/a$ (where $a$ is the scattering length)\nare treated as small mass scales. Comparisons with phase shift data, however,\nreveal a pattern of gross violations of the theorems for all coefficients in\nboth the $^1S_0$ and $^3S_1$ channels. Analogous theorems are developed for the\nenergy dependence $\\epsilon$ parameter which describes $^3S_1 - ^3D_1$ mixing.\nThese theorems are also violated. These failures strongly suggest that the\nphysical value of $m_\\pi$ is too large for the chiral expansion to be valid in\nthis context. Comparisons of $m_\\pi$ with phenomenological scales known to\narise in the two-nucleon problem support this conjecture.", "category": "nucl-th" }, { "text": "Covariant kinetic theory for effective fugacity quasi particle model and\n first order transport coefficients for hot QCD matter: An effective relativistic kinetic theory has been constructed for an\ninteracting system of quarks, anti-quarks and gluons within a quasi-particle\ndescription of hot QCD medium at finite temperature and baryon chemical\npotential, where the interactions are encoded in the gluon and quark effective\nfugacities with non-trivial energy dispersions. The local conservations of\nstress-energy tensor and number current require the introduction of a mean\nfield term in the transport equation which produces non-vanishing contribution\nto the first order transport coefficients. Such contribution has been observed\nto be significant for the temperatures which are closer to the QCD transition\ntem- perature, however, induces negligible contributions beyond a few times the\ntransition temperature. As an implication, impact of the mean field\ncontribution on the the temperature dependence of the shear viscosity, bulk\nviscosity and thermal conductivity of a hot QCD medium in the presence of\nbinary, elastic collisions among the constituents, has been investigated.\nVisible effects have been observed for the temperature regime closer to the QCD\ntransition temperature.", "category": "nucl-th" }, { "text": "HFODD (v2.08k): User's Guide: We describe the input data and installation procedures of the code HFODD\n(v2.08k). The present write-up contains complete and comprehensive information\nthat has originally been given in five independent publications. It is enhanced\nby the subject index and indexes of variables, input-data keywords,\nsubroutines, and files that are used in this user guide.", "category": "nucl-th" }, { "text": "Pseudo-gauge dependence of quantum fluctuations of energy in a hot\n relativistic gas of fermions: Explicit expressions for quantum fluctuations of energy in subsystems of a\nhot relativistic gas of spin-$1/2$ particles are derived. The results depend on\nthe form of the energy-momentum tensor used in the calculations, which is a\nfeature described as pseudo-gauge dependence. However, for sufficiently large\nsubsystems the results obtained in different pseudo-gauges converge and agree\nwith the canonical-ensemble formula known from statistical physics. As\ndifferent forms of the energy-momentum tensor of a gas are a priori equivalent,\nour finding suggests that the concept of quantum fluctuations of energy in very\nsmall thermodynamic systems is pseudo-gauge dependent. On the practical side,\nthe results of our calculations determine a scale of coarse graining for which\nthe choice of the pseudo-gauge becomes irrelevant.", "category": "nucl-th" }, { "text": "Quenching of pairing gap at finite temperature in 184W: We extract pairing gap in $^{184}$W at finite temperature for the first time\nfrom the experimental level densities of $^{183}$W, $^{184}$W, and $^{185}$W\nusing \"thermal\" odd-even mass difference. We found the quenching of pairing gap\nnear the critical temperature $T_c = 0.47$ MeV in the BCS calculations. It is\nshown that the monopole pairing model with a deformed Woods-Saxon potential\nexplains the reduction of the pairing correlation using the partition function\nwith the number parity projection in the static path approximation plus\nrandom-phase approximation.", "category": "nucl-th" }, { "text": "New Three-Nucleon-Force Terms in the Three-Nucleon System: We include two new three-nucleon-force terms of pion-range - short-range form\nin our momentum-space calculations for the three-nucleon continuum. These two\nterms are expected by chiral perturbation theory to be non-negligible. We study\nthe effects of these terms in elastic neutron-deuteron scattering and pay\nspecial attention to the neutron vector analyzing power $A_y$.", "category": "nucl-th" }, { "text": "Kaon effective mass and energy from a novel chiral SU(3)-symmetric\n Lagrangian: A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons\nand antikaons in the nuclear medium, the ground state of dense matter and the\nkaon-nuclear interactions consistently.\n The saturation properties of nuclear matter are reproduced as well as the\nresults of the Dirac-Br\\\"{u}ckner theory. Our numerical results show that the\nkaon effective mass might be changed only moderately in the nuclear medium due\nto the highly non-linear density effects. After taking into account the\ncoupling between the omega meson and the kaon, we obtain similar results for\nthe effective kaon and antikaon energies as calculated in the\none-boson-exchange model while in our model the parameters of the kaon-nuclear\ninteractions are constrained by the SU(3) chiral symmetry.", "category": "nucl-th" }, { "text": "Low-momentum NN interactions and all-order summation of ring diagrams of\n symmetric nuclear matter: We study the equation of state for symmetric nuclear matter using a\nring-diagram approach in which the particle-particle hole-hole ($pphh$) ring\ndiagrams within a momentum model space of decimation scale $\\Lambda$ are summed\nto all orders. The calculation is carried out using the renormalized\nlow-momentum nucleon-nucleon (NN) interaction $V_{low-k}$, which is obtained\nfrom a bare NN potential by integrating out the high-momentum components beyond\n$\\Lambda$. The bare NN potentials of CD-Bonn, Nijmegen and Idaho have been\nemployed. The choice of $\\Lambda$ and its influence on the single particle\nspectrum are discussed. Ring-diagram correlations at intermediate momenta\n($k\\simeq$ 2 fm$^{-1}$) are found to be particularly important for nuclear\nsaturation, suggesting the necessity of using a sufficiently large decimation\nscale so that the above momentum region is not integrated out. Using\n$V_{low-k}$ with $\\Lambda \\sim 3$ fm$^{-1}$, we perform a ring-diagram\ncomputation with the above potentials, which all yield saturation energies\n$E/A$ and Fermi momenta $k_F^{(0)}$ considerably larger than the empirical\nvalues. On the other hand, similar computations with the medium-dependent\nBrown-Rho scaled NN potentials give satisfactory results of $E/A \\simeq -15$\nMeV and $k_F^{(0)}\\simeq 1.4$ fm$^{-1}$. The effect of this medium dependence\nis well reproduced by an empirical 3-body force of the Skyrme type.", "category": "nucl-th" }, { "text": "Evolution of particle density in high-energy pp collisions: We study the evolution of the particle density, dn/d\\eta at fixed \\eta with\nthe beam rapidity Y in the framework of string percolation model. Our main\nresults are: (i) The width of the \"plateau\" increases proportionally to Y, (ii)\nlimiting fragmentation is violated, and (iii) the particle density, reduces to\na step function.", "category": "nucl-th" }, { "text": "$\u03b1$-decay half-lives of superheavy nuclei with $Z=122-125$: For $\\alpha$ decay half-life calculations in this work, the Coulomb and\nproximity potential model with a new semiempirical formula for diffuseness\nparameter developed in previous work [Phys. Rev. C 100, 024601 (2019)] is used.\nThe present model in this work is compared with the generalized liquid-drop\nmodel (GLDM), universal decay law (UDL), and experimental half-lives in the\nregion $Z=104-118$. Next, the predicted half-lives of 51 superheavy nuclei\n(SHN) with $Z=122-125$ by the present model are compared with those of GLDM,\nand UDL. The present model is revealed to be more accurate in reproducing\nexperimental half-lives compared to GLDM and UDL. Moreover, it is found that\nthe predictions of the present model and UDL are highly consistent while GLDM\nlargely deviates from the other two. A study of the competition between\n$\\alpha$ decay and spontaneous fission (SF) shows that $\\alpha$ decay is the\ndominant mode. Among the studied SHN with $Z=122-125$, ${}^{295-307}122$ and\n${}^{314-320}125$ are identified as potential candidates whose half-lives are\nrelatively long enough to be experimentally detected in the future through\ntheir $\\alpha$-decay chains. The identified candidates are in good agreement\nwith other recent work.", "category": "nucl-th" }, { "text": "Power-law intensity distribution in $\u03b3$-decay cascades -- Nuclear\n Structure as a Scale-Free Random Network: By modeling the transition paths of the nuclear $\\gamma$-decay cascade using\na scale-free random network, we uncover a universal power-law distribution of\n$\\gamma$-ray intensity $\\rho_I(I) \\propto I^{-2}$, with $I$ the $\\gamma$-ray\nintensity of each transition. This property is consistently observed for all\ndatasets with a sufficient number of $\\gamma$-ray intensity entries in the\nNational Nuclear Data Center database, regardless of the reaction type or\nnuclei involved. In addition, we perform numerical simulations which support\nthe model's predictions of level population density.", "category": "nucl-th" }, { "text": "Superscaling in lepton-nucleus scattering: We suggest that superscaling analyses of few-GeV inclusive electron\nscattering from nuclei, both in the quasielastic peak and in the region where\nthe $\\Delta$-excitation dominates, allow one to make reliable predictions for\ncharge-changing neutrino reactions at energies of a few GeV, relevant for\nneutrino oscillation experiments.", "category": "nucl-th" }, { "text": "Finite size effect on Dissociation and Diffusion of chiral partners in\n Nambu-Jona-Lasinio model: Along with masses of pion and sigma meson modes, their dissociation into\nquark medium provide a detail spectral structures of the chiral partners.\nPresent article has studied a finite size effect on that detail structure of\nchiral partners by using the framework of Nambu-Jona-Lasinio model. Through\nthis dissociation mechanism, their diffusions and conductions are also studied.\nThe masses, widths, diffusion coefficients, conductivities of chiral partners\nare merged at different temperatures in restore phase of chiral symmetry, but\nmerging points of all are shifted in lower temperature, when one introduce\nfinite size effect into the picture. The strengths of diffusions and\nconductions are also reduced due to finite size consideration.", "category": "nucl-th" }, { "text": "Contributions of different neutron pairs in different approaches for\n neutrinoless double beta decay: The methods used till now to calculate the neutrinoless double beta decay\nmatrix elements are: the Quasiparticle Random Phase Approximation (QRPA), the\nShell Model (SM), the angular momentum projected Hartee-Fock-Bogoliubov\napproach (HFB) and the Interacting Boson Model (IBM). The different approaches\nare compared specifically concerning the the angular momenta and parities of\nthe neutron pairs, which are changed into two protons by the $0\\nu\\beta\\beta$\ndecay. The QRPA and SM involve about the same angular momentum and parity\nneutron pairs, while the HFB is restricted to $0^{+}, 2^{+}, 4^{+}, ...$, and\nIBM to $0^{+}$ and $2^{+}$ nucleon pairs. The differences in the seniority\ncontributions for the QRPA and the SM are discussed.", "category": "nucl-th" }, { "text": "Momentum transport away from a jet in an expanding nuclear medium: We study the transport dynamics of momenta deposited from jets in\nultrarelativistic heavy-ion collisions. Assuming that the high-energy partons\ntraverse expanding quark-gluon fluids and are subject to lose their energy and\nmomentum, we simulate dijet asymmetric events by solving relativistic\nhydrodynamic equations numerically without linearization in the fully\n(3+1)-dimensional coordinate. Mach cones are formed and strongly broadened by\nradial flow of the background medium. As a result, the yield of low-$p_{T}$\nparticles increases at large angles from the jet axis and compensates the dijet\nmomentum imbalance inside the jet-cone. This provides an intimate link between\nthe medium excitation by jets and results in dijet asymmetric events observed\nby the CMS Collaboration.", "category": "nucl-th" }, { "text": "Study of freeze-out dynamics of strange hadrons: We study the chemical freeze-out dynamics of strange particles ($K,\\,\n\\Lambda,\\, \\Sigma$) from a homogeneous and isotropically expanding hadronic\nsystem of $\\pi, K, \\rho, N, \\Lambda$ and $\\Sigma$ with zero net baryon density.\nWe use the momentum integrated Boltzmann equation and study their evolution\nover the bulk hadronic matter, a condition being similar to the one created at\ntop RHIC and LHC energies. The cross-sections, which are input to the\nequations, are taken either from phenomenological models or parameterized by\ncomparing against experimental data. From this microscopic calculation we find\nthat these strange particles freeze-out near transition temperature $\\approx\nT_c$ due to large relaxation time. The continuous cease of the inelastic\nprocesses due to gradual fall in the temperature and decrease in the number\ndensity, thus lead to early freeze out of strange hadrons $K, \\Lambda$ and\n$\\Sigma$ which happens sequentially near $T_c$. However, freeze-out of these\nstrange species near Tc appears as a sudden and simultaneous process, which is\nmostly predicted by thermal model while explaining the yield of identified\nparticles at RHIC and LHC energies.", "category": "nucl-th" }, { "text": "Chiral three-nucleon force and continuum for dripline nuclei and beyond: Three-nucleon force and continuum play important roles in reproducing the\nproperties of atomic nuclei around driplines. Therefore it is valuable to build\nup a theoretical framework where both effects can be taken into account to\nsolve the nuclear Schr\\\"odinger equation. To this end, in this letter, we have\nexpressed the chiral three-nucleon force within the continuum Berggren\nrepresentation, so that bound, resonant and continuum states can be treated on\nan equal footing in the complex-momentum space. To reduce the model dimension\nand computational cost, the three-nucleon force is truncated at the\nnormal-ordered two-body level and limited in the $sd$-shell model space, with\nthe residual three-body term being neglected. We choose neutron-rich oxygen\nisotopes as the test ground because they have been well studied experimentally,\nwith the neutron dripline determined. The calculations have been carried out\nwithin the Gamow shell model. The quality of our results in reproducing the\nproperties of oxygen isotopes around the neutron dripline shows the relevance\nof the interplay between three-nucleon force and the coupling to continuum\nstates. We also analyze the role played by the chiral three-nucleon force, by\ndissecting the contributions of the $2\\pi$ exchange, $1\\pi$ exchange and\ncontact terms.", "category": "nucl-th" }, { "text": "Deformation and cluster structures in $^{12}$C studied with\n configuration mixing using Skyrme interactions: We report an investigation of the structure of $^{12}$C nucleus employing a\nnewly developed configuration-mixing method. In the three-dimensional\ncoordinate-space representation, we generate a number of Slater determinants\nwith various correlated structures using the imaginary-time algorithm. We then\ndiagonalize a many-body Hamiltonian with the Skyrme interaction in the space\nspanned by the Slater determinants with parity and angular momentum\nprojections. Our calculation reasonably describes the ground and excited states\nof $^{12}$C nucleus, both for shell-model-like and cluster-like states. The\nexcitation energies and transition strengths of the ground-state rotational\nband are well reproduced. Negative parity excited states, $1_1^-$, $2_1^-$, and\n$3_1^-$, are also reasonably described. The second and third $0^+$ states,\n$0_2^+$ and $0_3^+$, appear at around 8.8 MeV and 15 MeV, respectively. The\n$0_2^+$ state shows a structure consistent with former results of the\n\\alpha-cluster models, however, the calculated radius of the $0_2^+$ state is\nsmaller than those calculations. The three-{\\alpha} linear-chain configuration\ndominates in the $0_3^+$ state.", "category": "nucl-th" }, { "text": "GLISSANDO: GLauber Initial-State Simulation AND mOre: GLISSANDO is a Glauber Monte-Carlo generator for early-stages of relativistic\nheavy-ion collisions, written in c++ and interfaced to Root. Several models are\nimplemented: the wounded-nucleon model, the binary collisions model, the mixed\nmodel, and the model with hot-spots. Subtleties of the distribution of nucleon\nin the nucleus are discussed. The original geometric distribution of sources in\nthe transverse plane can be superimposed with a statistical distribution\nsimulating the dispersion in the generated transverse energy in each individual\ncollision. The program generates inter alia the fixed axes (standard) and\nvariable-axes (participant) two-dimensional profiles of the density of sources\nin the transverse plane and their Fourier components. These profiles can be\nused in further analyses of physical phenomena, such as the the jet quenching,\nevent-by-event hydrodynamics, or analysis of the elliptic flow and its\nfluctuations. Characteristics of the event (multiplicities, eccentricities,\nFourier coefficients, etc.) are evaluated and stored in a file for further\noff-line studies. A number of scripts is provided for that purpose. Supplied\nvariants of the code can also be used for the proton-nucleus and\ndeuteron-nucleus collisions.", "category": "nucl-th" }, { "text": "Effects of triaxiality and pairing interaction on fission barriers of\n actinide nuclei studied by density-dependence relativistic mean-field theory: We employ density-dependent relativistic mean-field theory to study how the\ntriaxiality and pairing interaction affect the inner fission barriers of\nactinide nuclei. It was found that triaxiality reduced the inner fission\nbarriers and improved agreement with experimental values for many actinides.\nHowever, about 1-2 MeV discrepancy to the experimental values still remained\nfor some of the considered nuclei. Such a discrepancy could be made further\nsmaller by increasing the BCS pairing strength parameter. In this work, we\ndemonstrated that adjusting the paring strength was effective to reproduce the\nexperimental inner fission barriers as well as \"pairing rotational energy\" and\nbinding energy in a consistent manner for nuclei where the effect of the\ntriaxiality on the inner fission barriers was significant.", "category": "nucl-th" }, { "text": "Yrast band in the heavy $N = Z$ nucleus $^{88}$Ru: $\u03b1$-cluster\n approach: The yrast band in the heavy $N = Z$ nucleus $^{88}$Ru is studied in the\nframework of the $\\alpha$-cluster model in combination with double-folding\npotentials. It is found that the excitation energies of the yrast band in\n$^{88}$Ru can be nicely described within the $\\alpha$-cluster approach using a\nsmooth and mildly $L$-dependent adjustment of the potential strength. This\nresult is similar to well-established $\\alpha$-cluster states in nuclei with a\n(magic core $\\otimes$ $\\alpha$) structure. Contrary, the yrast bands in\nneighboring $N \\ne Z$ nuclei deviate from such a typical $\\alpha$-cluster\nbehavior. Finally, the $\\alpha$-cluster model predicts reduced transition\nstrengths of about 10 Weisskopf units for intraband transitions between\nlow-lying states in the yrast band of $^{88}$Ru.", "category": "nucl-th" }, { "text": "Density dependent magnetic field and the equation of state of hyperonic\n matter: We are interested on the effects, caused by strong variable density dependent\nmagnetic fields, on hyperonic matter, its symmetry energy, equations of state\nand mass-radius relations. The inclusion of the anomalous magnetic moment of\nthe particles involved in a stellar system is performed, and some results are\ncompared with the cases that do not take this correction under consideration.\nThe Lagrangian density used follows the nonlinear Walecka model plus the\nleptons subjected to an external magnetic field.", "category": "nucl-th" }, { "text": "Weak Magnetism Correction to Allowed Beta-decay for Reactor Antineutrino\n Spectra: The weak magnetism correction and its uncertainty to nuclear beta-decay play\na major role in determining the significance of the reactor neutrino anomaly.\nHere we examine the common approximation used for one-body weak magnetism in\nthe calculation of fission antineutrino spectra, wherein matrix elements of the\norbital angular momentum operator contribution to the magnetic dipole current\nare assumed to be proportional to those of the spin operator. Although we find\nthis approximation invalid for a large set of nuclear structure situations, we\nconclude that it is valid for the relevant allowed beta-decays between fission\nfragments. In particular, the uncertainty in the fission antineutrino due to\nthe uncertainty in the one-body weak magnetism correction is found to be less\nthan 1%. Thus, the dominant uncertainty from weak magnetism for reactor\nneutrino fluxes lies in the uncertainty in the two-body meson-exchange magnetic\ndipole current.", "category": "nucl-th" }, { "text": "Nuclear excitation cross section of $^{229}$Th via inelastic electron\n scattering: Nuclear excitation cross section of $^{229}$Th from the ground state to the\nlow-lying isomeric state via inelastic electron scattering is calculated, on\nthe level of Dirac distorted wave Born approximation. With electron energies\nbelow 100 eV, inelastic scattering is very efficient in the isomeric\nexcitation, yielding excitation cross sections on the order of 10$^{-27}$ to\n10$^{-26}$ cm$^2$. Systematic analyses are presented on elements affecting the\nexcitation cross section, including the ion-core potential, the relativistic\neffect, the knowledge of the reduced nuclear transition probabilities, etc.", "category": "nucl-th" }, { "text": "Neutrino-nucleus interactions in the T2K experiment: We present a study of neutrino-nucleus interactions at the T2K experiment\nbased on the GiBUU transport model. The aim of T2K is to measure $\\nu_e$\nappearance and $\\theta_{13}$, but it will also be able to do a precise\nmeasurement of $\\nu_\\mu$ disappearance. The former requires a good\nunderstanding of $\\pi^0$ production while the latter is closely connected with\na good understanding of quasielastic scattering. For both processes we\ninvestigate the influence of nuclear effects and particular final-state\ninteractions on the expected event rates taking into account the T2K detector\nsetup.", "category": "nucl-th" }, { "text": "High temperature phase of QCD: I give a brief overview of our present understanding of the high temperature\nphase of QCD, trying to clarify some of the theoretical issues involved in the\ncurrent discussions that emphasize the strongly coupled character of the\nquark-gluon plasma produced at RHIC.", "category": "nucl-th" }, { "text": "Measurement of the energy of the 8.3-eV isomer of 229mTh with\n photoelectric effect: It is proposed to use the photoelectric effect in the inner shells of the\n229Th atoms to refine the energy of the 8.3-eV isomer. The calculation was\nperformed using the Feinberg-Migdal shaking theory, which leads to the\nprobability of isomer formation up to several units of 10^-4 in the case of the\nK shell. As a result, two lines are predicted in the photoelectron spectrum,\ntheir separation energy providing the energy of the isomer. Other ways of using\nthe method to study the properties of the isomer are also discussed: through\nshaking during the formation of radioactive beams in storage rings, etc.\nMoreover, recording the effect in an experiment will provide the isomer's\npartial lifetime.", "category": "nucl-th" }, { "text": "Emergence of hydrodynamics in expanding relativistic plasmas: I consider a simple set of equations that govern the expansion of\nboost-invariant plasmas of massless particles. These equations describe the\ntransition from a collisionless regime at early time to hydrodynamics at late\ntime. Their mathematical structure encompasses all versions of second order\nhydrodynamics. We emphasize that the apparent success of Israel-Stewart\nhydrodynamics at early time has little to do with ``hydrodynamics'' proper, but\nrather with a particular feature of Israel-Stewart equations that allows them\nto effectively mimic the collisionless regime.", "category": "nucl-th" }, { "text": "Strangeness in nuclear physics: Extensions of nuclear physics to the strange sector are reviewed, covering\ndata and models of Lambda and other hypernuclei, multi-strange matter, and\nanti-kaon bound states and condensation. Past achievements are highlighted,\npresent unresolved problems discussed, and future directions outlined.", "category": "nucl-th" }, { "text": "Observation of the Mott Effect in Heavy Ion Collisions: Possibility of observing the Mott momentum in the distribution of the\ndeuterons produced in the process $p + n \\to d + \\gamma$, in the first stage of\na nuclear reaction is presented. The correlation of a hard photon with a\ndeuteron allows to select those deuterons produced at the beginning of a\nreaction.", "category": "nucl-th" }, { "text": "Shear viscosity to entropy density ratio of a relativistic Hagedorn\n resonance gas: The new state of matter produced at Relativistic Heavy Ion Collider reveals a\nstrongly coupled quark-gluon plasma with an extremely small shear viscosity to\nentropy density ratio eta/s. We calculate the eta/s of an equilibrated hadron\nmatter characterized by a relativistic hadron resonance gas with a Hagedorn\nmass spectrum that grows exponentially with the hadron mass. We find with\nincrease in temperature of the system the eta/s value decreases due to rapid\nincrease in the multiplicity of massive resonances. In the vicinity of the\ncritical temperature for deconfinement transition, the minimum value of eta/s\nin the Hagedorn resonance gas is found to be consistent with the current\nestimates for a strongly coupled quark-gluon plasma.", "category": "nucl-th" }, { "text": "On the dominance of J(P)=0(+) ground states in even-even nuclei from\n random two-body interactions: Recent calculations using random two-body interactions showed a preponderance\nof J(P)=0(+) ground states, despite the fact that there is no strong pairing\ncharacter in the force. We carry out an analysis of a system of identical\nparticles occupying orbits with j=1/2, 3/2 and 5/2 and discuss some general\nfeatures of the spectra derived from random two-body interactions. We show that\nfor random two-body interactions that are not time-reversal invariant the\ndominance of 0(+) states in this case is more pronounced, indicating that\ntime-reversal invariance cannot be the origin of the 0(+) dominance.", "category": "nucl-th" }, { "text": "Multiplicity Fluctuations in Limited Segments of Momentum Space in\n Statistical Models: Multiplicity fluctuations in limited segments of momentum space are\ncalculated for a classical pion gas within the statistical model. Results for\nthe grand canonical, canonical, and micro-canonical ensemble are obtained,\ncompared and discussed. We demonstrate that even in the large volume limit\ncorrelations between macroscopic subsystems due to energy and momentum\nconservation persist. Based on the micro-canonical formulation we make\nqualitative predictions for the rapidity and transverse momentum dependence of\nmultiplicity fluctuations. The resulting effects are of similar magnitude as\nthe predicted enhancement due to a phase transition from a quark-gluon plasma\nto a hadron gas phase, or due to the critical point of strongly interacting\nmatter, and qualitatively agree with recently published preliminary\nmultiplicity fluctuation data of the NA49 SPS experiment.", "category": "nucl-th" }, { "text": "Covariant density functional analysis of shape evolution in $N =40$\n isotones: The structure of low-lying excitation states of even-even $N=40$ isotones is\nstudied using a five-dimensional collective Hamiltonian with the collective\nparameters determined from the relativistic mean-field plus BCS method with the\nPC-PK1 functional in the particle-hole channel and a separable paring force in\nthe particle-particle channel. The theoretical calculations can reproduce not\nonly the systematics of the low-lying states along the isotonic chain but also\nthe detailed structure of the spectroscopy in a single nucleus. We find a\npicture of spherical-oblate-prolate shape transition along the isotonic chain\nof $N=40$ by analyzing the potential energy surfaces. The coexistence of\nlow-lying excited $0^+$ states has also been shown to be a common feature in\nneutron-deficient $N=40$ isotones.", "category": "nucl-th" }, { "text": "Mixed phases during the phase transitions: Quest for a new form of matter inside compact stars compels us to examine the\nthermodynamical properties of the phase transitions. We closely consider the\nfirst-order phase transitions and the phase equilibrium on the basis of the\nGibbs conditions, taking the liquid-gas phase transition in asymmetric nuclear\nmatter as an example. Characteristic features of the mixed phase are figured\nout by solving the coupled equations for mean-fields and densities of\nconstituent particles self-consistently within the Thomas-Fermi approximation.\nThe mixed phase is inhomogeneous matter composed of two phases in equilibrium;\nit takes a crystalline structure with a unit of various geometrical shapes,\ninside of which one phase with a characteristic shape, called \"pasta\", is\nembedded in another phase by some volume fraction. This framework enables us to\nproperly take into account the Coulomb interaction and the interface energy,\nand thereby sometimes we see the mechanical instability of the geometric\nstructures of the mixed phase. Thermal effect on the liquid-gas phase\ntransition is also elucidated.\n Similarly hadron-quark deconfinement transition is studied in hyperonic\nmatter, where the neutrino-trapping effect as well as the thermal effect is\ndiscussed in relation to the properties of the mixed phase. Specific features\nof the mixed phase are elucidated and the equation of state is presented.", "category": "nucl-th" }, { "text": "Lattice Gauge Theory - QCD from Quarks to Hadrons: Lattice Gauge Theory enables an ab initio study of the low-energy properties\nof Quantum Chromodynamics, the theory of the strong interaction. I begin these\nlectures by presenting the lattice formulation of QCD, and then outline the\nbenchmark calculation of lattice QCD, the light-hadron spectrum. I then proceed\nto explore the predictive power of lattice QCD, in particular as it pertains to\nhadronic physics. I will discuss the spectrum of glueballs, exotics and excited\nstates, before investigating the study of form factors and structure functions.\nI will conclude by showing how lattice QCD can be used to study multi-hadron\nsystems, and in particular provide insight into the nucleon-nucleon\ninteraction.", "category": "nucl-th" }, { "text": "Isoscalar-Isovector Interferences in $\u03c0N \\to N e^+ e^-$ Reactions as\n a Probe of Baryon Resonance Dynamics: The isoscalar-isovector ($\\rho-\\omega$) interferences in the exclusive\nreactions $\\pi^- p \\to n e^+ e^-$ and $\\pi^+ n \\to p e^+ e^-$ near the $\\omega$\nthreshold leads to a distinct difference of the dielectron invariant mass\ndistributions depending on beam energy. The strength of this effect is\ndetermined by the coupling of resonances to the nucleon vector-meson channels\nand other resonance properties. Therefore, a combined analysis of these\nreactions can be used as a tool for determining the baryon resonance dynamics.", "category": "nucl-th" }, { "text": "Hadronic matter compressibility from event-by-event analysis of\n heavy-ion collisions: We propose a method to measure the hadronic matter compressibility by means\nof the event-by-event analysis of heavy-ion collisions at high energies. The\nmethod, which utilizes the thermodynamical relation between the compressibility\nand the particle number fluctuations, requires a simultaneous measurement of\nthe particle source size, temperature and particle multiplicity.", "category": "nucl-th" }, { "text": "Modeling Nuclear Properties with Support Vector Machines: We have made initial studies of the potential of support vector machines\n(SVM) for providing statistical models of nuclear systematics with demonstrable\npredictive power. Using SVM regression and classification procedures, we have\ncreated global models of atomic masses, beta-decay halflives, and ground-state\nspins and parities. These models exhibit performance in both data-fitting and\nprediction that is comparable to that of the best global models from nuclear\nphenomenology and microscopic theory, as well as the best statistical models\nbased on multilayer feedforward neural networks.", "category": "nucl-th" }, { "text": "Impact of level densities and $\u03b3$-strength functions on $r$-process\n simulations: Studies attempting to quantify the sensitivity of the $r$-process abundances\nto nuclear input have to cope with the fact that the theoretical models they\nrely on, rarely come with confidence intervals. This problem has been dealt\nwith by either estimating these intervals and propagating them statistically to\nthe final abundances using reaction networks within simplified astrophysical\nmodels, or by running more realistic astrophysical simulations using different\nnuclear-physics models consistently for all the involved nuclei. Both of these\napproaches have their strengths and weaknesses. In this work, we run\n$r$-process calculations for five trajectories using 49 different\nneutron-capture rate models. Our results shed light on the importance of taking\ninto account shell effects and pairing correlations in the network\ncalculations.", "category": "nucl-th" }, { "text": "Quark contribution to the nucleon polarizabilities and three-body forces: We study the response of the nucleon, as a system of three bound\n(constituent) non relativistic quarks, to external (quasi static) electric and\nmagnetic fields. The approach, based on a sum rule technique, is applied to a\nlarge class of two and three-body interquark potentials. Lower and upper bounds\nto the electric polarizability and para-magnetic susceptibility are explicitly\ncalculated within a large variety of constituent models and their values\nrelated to the features of the interquark interaction picture. The r\\^ole of\nthree-body forces is investigated in details as well as the effects of SU(6)\nbreaking terms in the potential model. Our results can be used to extract the\nmesonic contributions to the static polarizabilty and susceptibility. The quark\ndegrees of freedom give a quite sizeable contributions to both and the meson\ncloud accounts roughly for 30% and 60% of the electric proton and neutron\npolarizability respectively. The quark contribution to the paramagnetic\nsusceptibility is even higher and the mesonic effects are rather uncertain.", "category": "nucl-th" }, { "text": "Flavor and Charge Symmetry in the Parton Distributions of the Nucleon: Recent calculations of charge symmetry violation(CSV) in the valence quark\ndistributions of the nucleon have revealed that the dominant symmetry breaking\ncontribution comes from the mass associated with the spectator quark\nsystem.Assuming that the change in the spectator mass can be treated\nperturbatively, we derive a model independent expression for the shift in the\nparton distributions of the nucleon. This result is used to derive a relation\nbetween the charge and flavor asymmetric contributions to the valence quark\ndistributions in the proton, and to calculate CSV contributions to the nucleon\nsea. The CSV contribution to the Gottfried sum rule is also estimated, and\nfound to be small.", "category": "nucl-th" }, { "text": "The sound generated by a fast parton in the quark-gluon plasma is a\n crescendo: The total energy deposited into the medium per unit length by a fast parton\ntraversing a quark-gluon plasma is calculated. We take the medium excitation\ndue to collisions to be given by the well known expression for the collisional\ndrag force. The parton's radiative energy loss contributes to the energy\ndeposition because each radiated gluon acts as an additional source of\ncollisional energy loss in the medium. In our model, this leads to a length\ndependence on the differential energy loss due to the interactions of radiated\ngluons with the medium. The final result, which is a sum of the primary and the\nsecondary contributions, is then treated as the coefficient of a local\nhydrodynamic source term. Results are presented for energy density wave induced\nby two fast, back-to-back partons created in an initial hard interaction.", "category": "nucl-th" }, { "text": "Bethe-Salpeter approach with the separable interaction for the deuteron: Recent developments of the covariant Bethe-Salpeter (BS) approach with the\nuse of the separable interaction for the deuteron are reviewed. It is shown\nthat the BS formalism allows a covariant description of various electromagnetic\nreactions like the lepton-deuteron scattering, deuteron electro-disintegration,\ndeep inelastic scattering (DIS) of leptons on light nuclei. The procedure of\nthe construction of the separable nucleon-nucleon (NN) interaction is\ndiscussed. The BS formalism facilitates analysis of the role of the P-waves\n(negative energy components) in the electromagnetic properties of the deuteron\nand its comparison with the nonrelativistic results. Furthermore the covariant\nBS approach makes it possible to analyze DIS of leptons from the deuteron in a\nmodel independent way and to extend the formalism to DIS reactions on the light\nnuclei.", "category": "nucl-th" }, { "text": "A deformed QRPA formalism for single and two-neutrino double beta decay: We use a deformed QRPA formalism to describe simultaneously the energy\ndistributions of the single beta Gamow-Teller strength and the two-neutrino\ndouble beta decay matrix elements. Calculations are performed in a series of\ndouble beta decay partners with A = 48, 76, 82, 96, 100, 116, 128, 130, 136 and\n150, using deformed Woods-Saxon potentials and deformed Skyrme Hartree-Fock\nmean fields. The formalism includes a quasiparticle deformed basis and residual\nspin-isospin forces in the particle-hole and particle-particle channels. We\ndiscuss the sensitivity of the parent and daughter Gamow-Teller strength\ndistributions in single beta decay, as well as the sensitivity of the double\nbeta decay matrix elements to the deformed mean field and to the residual\ninteractions. Nuclear deformation is found to be a mechanism of suppression of\nthe two-neutrino double beta decay. The double beta decay matrix elements are\nfound to have maximum values for about equal deformations of parent and\ndaughter nuclei. They decrease rapidly when differences in deformations\nincrease. We remark the importance of a proper simultaneous description of both\ndouble beta decay and single Gamow-Teller strength distributions. Finally, we\nconclude that for further progress in the field it would be useful to improve\nand complete the experimental information on the studied Gamow-Teller strengths\nand nuclear deformations.", "category": "nucl-th" }, { "text": "Triple-Gluon and Triple-Quark Elastic Scatterings and Early\n Thermalization: Three-gluon to three-gluon scatterings lead to rapid thermalization of gluon\nmatter created in central Au-Au collisions at RHIC energies. Thermalization of\nquark matter is studied from three-quark to three-quark scatterings.", "category": "nucl-th" }, { "text": "Strangeness in the cores of neutron stars: The measurement of the mass 1.97 +/- 0.04 M_sun for PSR J1614-2230 provides a\nnew constraint on the equation of state and composition of matter at high\ndensities. In this contribution we investigate the possibility that the dense\ncores of neutron stars could contain strange quarks either in a confined state\n(hyperonic matter) or in a deconfined one (strange quark matter) while\nfulfilling a set of constraints including the new maximum mass constraint. We\naccount for the possible appearance of hyperons within an extended version of\nthe density-dependent relativistic mean-field model, including the phi-meson\ninteraction channel. Deconfined quark matter is described by the color\nsuperconducting three-flavor NJL model.", "category": "nucl-th" }, { "text": "Manifestly-covariant chiral PT calculation of nucleon Compton scattering: We compute the Compton scattering off the nucleons in the framework of\nmanifestly covariant baryon chiral perturbation theory (B$\\chi$PT). The results\nfor observables differ substantially from the corresponding calculations in\nheavy-baryon chiral perturbation theory (HB$\\chi$PT), most appreciably in the\nforward kinematics. We verify that the covariant $p^3$ result fulfills the\nforward-Compton-scattering sum rules. We also explore the effect of the\n$\\Delta$(1232) resonance at order $p^4/\\varDelta$, with $\\varDelta\\approx 300$\nMeV, the resonance excitation energy. We find that the substantial effect of\nthe $\\Delta$-excitation on the nucleon polarizabilities can naturally be\naccommodated in the manifestly covariant calculation.", "category": "nucl-th" }, { "text": "Induced pseudoscalar form factor of the nucleon at two-loop order in\n chiral perturbation theory: We calculate the imaginary part of the induced pseudoscalar form factor of\nthe nucleon $G_P(t)$ in the framework of two-loop heavy baryon chiral\nperturbation theory. The effect of the calculated three-pion continuum on the\npseudoscalar constant $g_P = (m_\\mu/2M) G_P(t=-0.877m_\\mu^2)$ measurable in\nordinary muon capture $\\mu^-p\\to \\nu_\\mu n$ turns out to be negligibly small.\nPossible contributions from counterterms at two-loop order are numerically\nsmaller than the uncertainty of the dominant pion-pole term proportional to the\npion-nucleon coupling constant $g_{\\pi N}= 13.2\\pm 0.2$. We conclude that a\nsufficiently accurate representation of the induced pseudoscalar form factor of\nthe nucleon at low momentum transfers $t$ is given by the sum of the pion-pole\nterm and the Adler-Dothan-Wolfenstein term: $G_P(t) = 4g_{\\pi N} M f_\\pi/\n(m_\\pi^2 -t)- 2g_A M^2 < r_A^2 >/3$, with $ = (0.44 \\pm 0.02)$ fm$^2$\nthe axial mean square radius of the nucleon.", "category": "nucl-th" }, { "text": "Microscopic calculation of the wobbling excitations by using the\n Woods-Saxon potential as a nuclear mean-field: The wobbling excitations of the triaxial superdeformed (TSD) bands in the Lu\nand Hf region are studied by the microscopic framework of the cranked\nmean-field and the random-phase approximation (RPA). In contrast to the\nprevious works, where the Nilsson potential was used, the more realistic\nWoods-Saxon potential is employed as a nuclear mean-field. The wobbling-like\nRPA solutions have been found systematically in the nuclei studied and their\ncharacteristic properties are investigated in details. This confirms the\nwobbling phonon excitations in TSD nuclei from the microscopic calculations.\nThe result of $B(E2)$ values indicates that the triaxial deformation is\nincreasing as a function of spin in the observed TSD bands in $^{163}$Lu.", "category": "nucl-th" }, { "text": "Search for Quasi Bound $\u03b7$ Mesons: The search for a quasi bound $\\eta$ meson in atomic nuclei is reviewed. This\ntentative state is studied theoretically as well as experimentally. The theory\nstarts from elastic $\\eta$ nucleon scattering which is derived from production\ndata within some models. From this interaction the $\\eta$ nucleus interaction\nis derived. Model calculations predict binding energies and widths of the quasi\nbound state. Another method is to derive the $\\eta$ nucleus interaction from\nexcitation functions of $\\eta$ production experiments. The $s$ wave interaction\nis extracted from such data via final state interaction theorem. We give the\nderivation of $s$ wave amplitudes in partial wave expansion and in helicity\namplitudes and their relation to observables. Different experiments extracting\nthe final state interaction are discussed as are production experiments. So far\nonly three experiments give evidence for the existence of the quasi bound\nstate: a pion double charge exchange experiment, an effective mass measurement,\nand a transfer reaction at recoil free kinematics with observation of the decay\nof the state.", "category": "nucl-th" }, { "text": "Bulk properties of nuclear matter in the relativistic Hartree\n approximation with cut-off regularization: A method of cut-off regularization is proposed to evaluate vacuum corrections\nin nuclear matter in the framework of the Hartree approximation. Bulk\nproperties of nuclear matter calculated by this method are a good agreement\nwith results analyzed by empirical values. The vacuum effect is quantitatively\nevaluated through a cut-off parameter and its role for saturation property and\ncompressional properties is clarified.", "category": "nucl-th" }, { "text": "Spherical to deformed shape transition in the nucleon-pair shell model: A study of the shape transition from spherical to axially deformed nuclei in\nthe even Ce isotopes using the nucleon-pair approximation of the shell model is\nreported. As long as the structure of the dominant collective pairs is\ndetermined using a microscopic framework appropriate to deformed nuclei, the\nmodel is able to produce a shape transition. However, the resulting transition\nis too rapid, with nuclei that should be transitional being fairly well\ndeformed, perhaps reflecting the need to maintain several pairs with each\nangular momentum.", "category": "nucl-th" }, { "text": "An analytic hydrodynamical model of rotating 3D expansion in heavy-ion\n collisions: A new exact and analytic solution of non-relativistic fireball hydrodynamics\nis presented. It describes an expanding triaxial ellipsoid that rotates around\none of its principal axes. The observables are calculated using simple analytic\nformulas. Azimuthal oscillation of the off-diagonal Bertsch-Pratt radii of\nBose-Einstein correlations as well as rapidity dependent directed and third\nflow measurements provide means to determine the magnitude of the rotation of\nthe fireball. Observing this rotation and its dependence on collision energy\nmay lead to new information on the equation of state of the strongly\ninteracting quark gluon plasma produced in high energy heavy ion collisions.", "category": "nucl-th" }, { "text": "Possible bound nuclei beyond the two-neutron drip line in the\n $50\\leqslant Z \\leqslant 70$ region: Possible bound nuclei beyond the two-neutron drip line in the $50\\leqslant Z\n\\leqslant 70$ region are investigated by using the deformed relativistic\nHartree-Bogoliubov theory in continuum with density functional PC-PK1. Bound\nnuclei beyond the drip lines of $_{56}$Ba, $_{58}$Ce, $_{62}$Sm, $_{64}$Gd and\n$_{66}$Dy are predicted, forming peninsulas of stability in nuclear landscape.\nNear these peninsulas, several multi-neutron emitters are predicted. The\nunderlying mechanism of the peninsulas of stability is investigated by studying\nthe total energy, Fermi surface, quadrupole deformation and the single-neutron\nspectrum in the canonical basis. It is found that the deformation effect is\ncrucial for forming the peninsulas of stability, and pairing correlations are\nalso essential in specific cases. The dependence on the deformation evolution\nis also discussed. The decay rates of multi-neutron radioactivity in Ba and Sm\nisotopic chains are estimated by using the direct decay model.", "category": "nucl-th" }, { "text": "Non-flow effects in three-particle mixed-harmonic azimuthal correlations\n in small collision systems: The Multi-particle technique has been used to unravel the nature of the\nlong-range collectivity in small collision systems. A large three-particle\nmixed-harmonic correlation signal was recently observed by the ATLAS\nCollaboration, but the role of non-flow correlations is not yet studied. We\nestimate the influence of non-flow correlations to the three-particle\ncorrelators in $pp$ and $p$+Pb collisions using PYTHIA and HIJING models, and\ncompare with the ATLAS results. The large non-flow effects from the jet and\ndijet production is found to be largely suppressed in $p$+Pb collisions using\nthe subevent cumulant method by calculating the azimuthal correlation between\ntwo or more longitudinal pseudorapidity ranges. Depending on the experimental\nsubevent method, however, the non-flow effects may still be significant in $pp$\ncollisions.", "category": "nucl-th" }, { "text": "Spectrum of resonance states in $^6$He. Experimental and theoretical\n analysis: We explore the structure of resonance states in $^{6}$He by experimental and\ntheoretical methods. We present the results of experimental investigations of\nthe three-body continuous spectrum of $^{6}$He. For this aim, we use the\nreaction $^{3}$H$( \\alpha,p\\alpha)nn$, which is induced by the interaction of\nalpha-particles with a triton at the beam energy $E_{\\alpha} =$~67.2 MeV. The\ntheoretical analysis of the resonance structure in $^{6}$He is carried out\nwithin the framework of a three-cluster microscopic model. The model exploits\nthe hyperspherical harmonics to describe the intercluster dynamics. The set of\nnew resonance states is discovered by the experimental and theoretical methods.\nThe energy, width, and dominant decay channels of resonances are determined.The\nobtained results are compared in detail with the results of different\ntheoretical models and experiments as well.", "category": "nucl-th" }, { "text": "J/\u03c8$ Gluonic Dissociation Revisited : III. Effects of Transverse\n Hydrodynamic Flow: In a recent paper [Eur. Phys. J {\\bf C 44}, 567 (2005)] we developed a very\ngeneral formulation to take into account explicitly the effects of hydrodynamic\nflow profile on the gluonic breakup of $J/\\psi$'s produced in an equilibrating\nquark-gluon plasma. Here we apply that formulation to the case when the medium\nis undergoing cylindrically symmetric {\\it transverse} expansion starting from\nRHIC or LHC initial conditions. Our algebraic and numerical estimates\ndemonstrate that the transverse expansion causes enhancement of local gluon\nnumber density $\\ng$, affects the $\\pt$-dependence of the average dissociation\nrate $\\tilg$ through a partial-wave interference mechanism, and makes the\nsurvival probability $\\spt$ to change with $\\pt$ very slowly. Compared to the\nprevious case of longitudinal expansion the new graph of $\\spt$ is pushed up at\nLHC, but develops a rich structure at RHIC, due to a competition between the\ntransverse catch-up time and plasma lifetime.", "category": "nucl-th" }, { "text": "Structural Properties of Finite and Infinite Nuclear Systems and Related\n Phenomena: In the present thesis, we have carried a thorough investigation of nuclear\nstructure properties. We start our investigation from the study of the magic\nproperty of nucleus in the super -heavy region. We know the magic combination\nof proton and neutron in the light and medium heavy region. But in the\nsuper-heavy region, it is still unclear. We applied SEI (simple effective\ninteraction ) and RMF (relativistic mean field ) formalism with a different\nparameter sets to predict the magic combinations and it turned out Z=114, 120,\n126 with N=184. We have also studied theisoscalar giant monopole resonance\nenergy of nucleus of Z=114, 120,126, with scaling and constrained method using\nRETF formalism. Isoscalar giant monopole resonance (ISGMR) is also known as the\nbreathing mode. We have a developed a new constrained type calculation for the\nISGMR and IVGDR. Effects of delta meson on the neutron system also discuses\nextensively.", "category": "nucl-th" }, { "text": "A stabilized pairing functional: We propose a modified pairing functional for nuclear structure calculations\nwhich avoids the abrupt phase transition between pairing and non-pairing\nstates. The intended application is the description of nuclear collective\nmotion where the smoothing of the transition is compulsory to remove\nsingularities. The stabilized pairing functional allows a thoroughly\nvariational formulation, unlike the Lipkin-Nogami (LN) scheme which is often\nused for the purpose of smoothing. First applications to nuclear ground states\nand collective excitations prove the reliability and efficiency of the proposed\nstabilized pairing.", "category": "nucl-th" }, { "text": "The Narrowing of Charge Balance Function and Hadronization Time in\n Relativistic Heavy Ion Collisions: The widths of charge balance function in high energy hadron-hadron and\nrelativistic heavy ion collisions are studied using the Monte Carlo generators\nPYTHIA and AMPT, respectively. The narrowing of balance function as the\nincrease of multiplicity is found in both cases. The mean parton-freeze-out\ntime of a heavy-ion-collision event is used as the characteristic hadronization\ntime of the event. It turns out that for a fixed multiplicity interval the\nwidth of balance function is consistent with being independent of hadronization\ntime.", "category": "nucl-th" }, { "text": "Mass dependence of short-range correlations in nuclei and the EMC effect: An approximate method to quantify the mass dependence of the number of\ntwo-nucleon (2N) short-range correlations (SRC) in nuclei is suggested. The\nproposed method relies on the concept of the \"local nuclear character\" of the\nSRC. We quantify the SRC and its mass dependence by computing the number of\nindependent-particle model (IPM) nucleon pairs in a zero relative orbital\nmomentum state. We find that the relative probability per nucleon for 2N SRC\nfollows a power law as a function of the mass number $A$. The predictions are\nconnected to measurements which provide access to the mass dependence of SRC.\nFirst, the ratio of the inclusive inelastic electron scattering cross sections\nof nuclei to $^{2}$H at large values of the Bjorken variable. Second, the EMC\neffect, for which we find a linear relationship between its magnitude and the\npredicted number of SRC-prone pairs.", "category": "nucl-th" }, { "text": "Study of the neutron and proton capture reactions 10,11b(n, g), 11b(p,\n g), 14c(p, g), and 15n(p, g) at thermal and astrophysical energies: We have studied the neutron-capture reactions 10,11B(n, g) and the role of\nthe 11B(n, g) reaction in seeding r-process nucleosynthesis. The possibility of\nthe description of the available experimental data for cross sections of the\nneutron capture reaction on 10B at thermal and astrophysical energies, taking\ninto account the resonance at 475 keV, was considered within the framework of\nthe modified potential cluster model (MPCM) with forbidden states and\naccounting for the resonance behavior of the scattering phase shifts. In the\nframework of the same model the possibility of describing the available\nexperimental data for the total cross sections of the neutron radiative capture\non 11B at thermal and astrophysical energies were considered with taking into\naccount the 21 and 430 keV resonances. Description of the available\nexperimental data on the total cross sections and astrophysical S-factor of the\nradiative proton capture on 11B to the ground state of 12C was treated at\nastrophysical energies. The possibility of description of the experimental data\nfor the astrophysical S-factor of the radiative proton capture on 14C to the\nground state of 15N at astrophysical energies, and the radiative proton capture\non 15N at the energies from 50 to 1500 keV was considered in the framework of\nthe MPCM with the classification of the orbital states according to Young\ntableaux. It was shown that, on the basis of the M1 and the E1 transitions from\ndifferent states of the p15N scattering to the ground state of 16O in the p15N\nchannel, it is quite succeed to explain general behavior of the S-factor in the\nconsidered energy range in the presence of two resonances.", "category": "nucl-th" }, { "text": "Kinematic Moment of Inertia of e-e Rare Earths Nuclei: The kinematic moment of inertia of the rare earth even-even nuclei was\ncalculated using three parametric energy based expression. The plot of\nkinematic moment of inertia versus nuclear spin shows a better sensitivity to\nback bending than energy plot.", "category": "nucl-th" }, { "text": "Effect of revised $R_n$ measurements on extended Gari-Krumpelmann model\n fits to nucleon electromagnetic form factors: The extended Gari-Krumpelmann (GK) model of nucleon electromagnetic form\nfactors, in which the $\\rho$, $\\rho'$, $\\omega$, $\\omega'$ and $\\phi$ vector\nmeson pole contributions evolve at high momentum transfer to conform to the\npredictions of perturbative QCD (pQCD), was recently shown to provide a very\ngood overall fit to all the nucleon electromagnetic form factor (emff) data,\nincluding the preliminary $R_p$ and $R_n$ polarization data available in 2002,\nbut excluding the older $G_{Ep}$ and $G_{En}$ differential cross section data\nthat was inconsistent with the $R_p$ and $R_n$ data. The recently published\nfinal version of the polarization data of the electric to magnetic ratio $R_p$\ndiffers little from the preliminary values for the former, but the new values\nof $R_n$ are midway between the preliminary values and those inferred from the\ndifferential cross section data and the Rosenbluth separation. A new fit of the\nparameters of the same model has been made with the final $R_p$ and $R_n$ data\nreplacing the preliminary values and the addition of some new $R_n$ and\n$G_{Mn}$ data. Again there is a good fit to all the data when excluding the\ndifferentialcross section data that is inconsistent with the polarization data.\nThis includes a very good fit of the $R_p$ data, which was not possible when\nthe differential cross section $G_(En)$ data was used in place of the\npolarization $R_n$ data. Thus the change between the preliminary and final\n$R_n$ data, while substantial, has not impeded the good simultaneous fit to the\nneutron and proton data. The parameters, fit to the data and predictions of the\nnew model are compared to those of the previous models. Low momentum structures\nthat appear in some data analyses are partially reproduced by the model.", "category": "nucl-th" }, { "text": "A New Renormalization Group for Hamiltonian Field Theory: The Schrodinger equation with a two-dimensional delta-function potential is a\nsimple example of an asymptotically free theory that undergoes dimensional\ntransmutation. Renormalization requires the introduction of a mass scale, which\ncan be lowered perturbatively until an infrared cutoff produced by\nnon-perturbative effects such as bound state formation is encountered. We\noutline the effective field theory and similarity renormalization group\ntechniques for producing renormalized cutoff hamiltonians, and illustrate the\ncontrol of logarithmic and inverse-power-law errors both techniques provide.", "category": "nucl-th" }, { "text": "Nuclear collective excitations using correlated realistic interactions:\n the role of explicit RPA correlations: We examine to which extent correlated realistic nucleon-nucleon interactions,\nderived within the Unitary Correlation Operator Method (UCOM), can describe\nnuclear collective motion in the framework of first-order random-phase\napproximation (RPA). To this end we employ the correlated Argonne V18\ninteraction in calculations within the so-called \"Extended\" RPA (ERPA) and\ninvestigate the response of closed-shell nuclei. The ERPA is a renormalized RPA\nversion which considers explicitly the depletion of the Fermi sea due to\nlong-range correlations and thus allows us to examine how these affect the\nexcitation spectra. It is found that the effect on the properties of giant\nresonances is rather small. Compared to the standard RPA, where excitations are\nbuilt on top of the uncorrelated Hartree-Fock (HF) ground state, their centroid\nenergies decrease by up to 1 MeV, approximately, in the isovector channel. The\nisoscalar response is less affected in general. Thus, the disagreement between\nour previous UCOM-based RPA calculations and the experimental data are to be\nattributed to other effects, mainly to a residual three-body force and\nhigher-order configurations. Ground-state properties obtained within the ERPA\nare compared with corresponding HF and perturbation-theory results and are\ndiscussed as well. The ERPA formalism is presented in detail.", "category": "nucl-th" }, { "text": "The Maximum Lifetime of the Quark-Gluon Plasma: The width $\\Delta T$ of the deconfinement transition region is shown to\ninfluence strongly the flow structure in the (Landau-) hydrodynamical expansion\nof a quark-gluon plasma. For a sharp first order transition ($\\Delta T=0$) the\nmixed phase is rather long-lived, with a lifetime that has a maximum when the\ninitial energy density is at the phase boundary between mixed and pure\nquark-gluon matter. For increasing $\\Delta T$, however, the lifetime decreases\nrapidly. Hadronic matter, however, remains long-lived as a consequence of the\nrapid change in the degrees of freedom in the transition region and the\ncorresponding ``softening'' of the equation of state.", "category": "nucl-th" }, { "text": "A Poincar\u00e9-covariant current operator for interacting systems and\n deuteron electromagnetic form factors: In front-form dynamics a current operator for systems of interacting\nparticles, which fulfills Poincar\\'e, parity and time reversal covariance,\ntogether with hermiticity, can be defined. The electromagnetic form factors can\nbe extracted without any ambiguity and in the elastic case the continuity\nequation is automatically satisfied. Applications to the calculation of\ndeuteron form factors are presented, and the effects of different\nnucleon-nucleon interactions, as well as of different nucleon form factors are\ninvestigated.", "category": "nucl-th" }, { "text": "Neutral Meson Photoproduction in $SU_f(3)$ $\u03c7$PT: We present the results for the electric dipole amplitude for $\\gamma N \\to\n\\pi^0 N$ at threshold at the $O(p^2)$ level in SU$_f$(3) chiral perturbation\ntheory. We find that the SU$_f$(3) results differ only slightly from the\nSU$_f$(2) results. At the $O(p^3)$ level one encounters new, unknown\ncounterterms to fix which one is likely to need the threshold photoproduction\ndata themselves, thus losing predictive power. We suggest, instead, that the\n{\\it difference} between the proton and neutron $\\pi^0$ photoproduction\namplitudes may provide a test of the convergence properties of the $\\chi$PT in\nthe present context. We urge that the neutron's electric dipole amplitude be\nmeasured.", "category": "nucl-th" }, { "text": "Structure of low-lying quadrupole states in nuclei near 132Sn: The properties of the low-lying 2^+ states in the even-even nuclei around\n132Sn are studied within the quasiparticle random phase approximation. Starting\nfrom a Skyrme interaction in the particle-hole channel and a density-dependent\nzero-range interaction in the particle-particle channel, we use the finite rank\nseparable approach in our investigation. It is found that the fourth 2^+ state\nin 132Te could be a good candidate for a mixed-symmetry state.", "category": "nucl-th" }, { "text": "Quantum field theoretic model of metastable resonant spin-singlet state\n of the np pair: The np pair in the spin-singlet state is treated as a Cooper np-pair within\nthe extension of the Nambu-Jona-Lasinio model of light nuclei, describing the\ndeuteron as a Cooper np-pair in the spin-triplet state. For the Cooper np-pair\nin the spin-singlet state we compute the binding energy and express the S-wave\nscattering length of np scattering in the spin-singlet state in terms of the\nbinding energy. The theoretical value of the S-wave scattering length of np\nscattering agrees well with the experimental data.", "category": "nucl-th" }, { "text": "The chiral restored quark stars can exist in the universe: In this paper, the equation of state (EOS) of deconfined quark stars is\nstudied in the framework of the two-flavor NJL model, and the self-consistent\nmean field approximation is employed by introducing a parameter $\\alpha$\ncombining the original Lagrangian and the Fierz-transformed Lagrangian,\n$\\mathcal{L}_R= (1-\\alpha)\\mathcal{L}+\\alpha\\mathcal{L}_F$, to measure the\nweights of different interaction channels. It is believed that the\ndeconfinement of phase transition happens along with the chiral phase\ntransition. Thus, due to the lack of description of confinement in the NJL\nmodel, the vacuum pressure is set to confine quarks at low densities, which is\nthe pressure corresponding to the critical point of chiral phase transition. We\nfind that deconfined quark stars can reach over two-solar-mass, and the bag\nconstant therefore shifts from $(130 ~\\mathrm{MeV})^4$ to $(150\n~\\mathrm{MeV})^4$ as $\\alpha$ grows. In addition, the tidal deformability\n$\\Lambda$ is yielded ranging from 253 to 482 along with the decrease of\n$~\\alpha$, which satisfies the astronomical constraint of $\\Lambda<800$ for\n1.4-solar-mass neutron stars.", "category": "nucl-th" }, { "text": "Potential turning points in cluster radioactivity: Effects of various nuclear interaction potentials on the decay lifetimes and\nthe turning points of the WKB action integral has been studied. The microscopic\nnuclear potential obtained by folding in the density distribution functions of\nthe two clusters with a realistic effective interaction has also been used to\ncalculate the turning points. Half lives of alpha and ^{20}O cluster emissions\nfrom ^{228}Th have been calculated within the superasymmetric fission model\nusing various phenomenological and the microscopic double folding potentials.\nCalculations of half lives with the microscopic double folding potentials are\nfound to be in good agreement with the observed experimental data. Present\ncalculations put the superasymmetric fission model on a firm theoretical basis.", "category": "nucl-th" }, { "text": "Systematic study of high-K isomers in the midshell Gd and Dy nuclei: High-K isomers are well known in the rare-earth region and provide unique\naccess to the high spin structures of the nuclei. With the current interest in\nthe study of neutron-rich rare-earth nuclei at Radioactive Ion Beam (RIB)\nfacilities, we present here theoretical results of the band structures of\nneutron-rich Gd and Dy nuclei, including the high K-isomers. Apart from the\nalready known K-isomers, we predict some more K-isomers and these are suggested\nfor future studies at RIB facilities. Self-consistent Deformed Hartree-Fock and\nAngular Momentum Projection theories are used to get the intrinsic structures,\nband-spectra and electromagnetic transitions probabilities of the ground band\nas well as bands based on isomers.", "category": "nucl-th" }, { "text": "The properties of \\bar{K} in the nuclear medium: The self-energy of the K^- meson in nuclear matter is calculated in a\nself-consistent microscopic approach, using a \\bar{K}N interaction obtained\nfrom the lowest-order meson-baryon chiral Lagrangian. The effective \\bar{K}N\ninteraction in the medium is derived by solving the coupled-channel\nBethe-Salpeter equation including Pauli blocking on the nucleons, mean-field\nbinding potentials for the baryons and the self-energy of the \\pi and \\bar{K}\nmesons. The incorporation of the self-consistent {\\bar K} self-energy in the\ndescription, in addition to the Pauli blocking effects, yields a weaker\nattractive in-medium {\\bar K}N interaction and a \\Lambda(1405) which dissolves\nfaster with increasing matter density, as a result of the {\\bar K} spectral\nfunction being spread out over a wide range of energies. These effects are\nfurther magnified when the intermediate pions are dressed.", "category": "nucl-th" }, { "text": "Symmetry broken and restored coupled-cluster theory I. Rotational\n symmetry and angular momentum: We extend coupled-cluster theory performed on top of a Slater determinant\nbreaking rotational symmetry to allow for the exact restoration of the angular\nmomentum at any truncation order. The main objective relates to the description\nof near-degenerate finite quantum systems with an open-shell character. As\nsuch, the newly developed many-body formalism offers a wealth of potential\napplications and further extensions dedicated to the ab initio description of,\ne.g., doubly open-shell atomic nuclei and molecule dissociation. The formalism,\nwhich encompasses both single-reference coupled cluster theory and projected\nHartree-Fock theory as particular cases, permits the computation of usual sets\nof connected diagrams while consistently incorporating static correlations\nthrough the highly non-perturbative restoration of rotational symmetry.\nInterestingly, the yrast spectroscopy of the system, i.e. the lowest energy\nassociated with each angular momentum, is accessed within a single calculation.\nA key difficulty presently overcome relates to the necessity to handle\ngeneralized energy {\\it and} norm kernels for which naturally terminating\ncoupled-cluster expansions could be eventually obtained. The present work\nfocuses on $SU(2)$ but can be extended to any (locally) compact Lie group and\nto discrete groups, such as most point groups. In particular, the formalism\nwill be soon generalized to $U(1)$ symmetry associated with particle number\nconservation. This is relevant to Bogoliubov coupled cluster theory that was\nrecently formulated and applied to singly open-shell nuclei.", "category": "nucl-th" }, { "text": "Compton scattering off proton in the third resonance region: Compton scattering off the proton in the third resonance region is analyzed\nfor the first time, owing to the full combined analysis of pion- and\nphoto-induced reactions in a coupled-channel effective Lagrangian model with\nK-matrix approximation. Two isospin $I=3/2$ resonances $D_{33}(1700)$ and\n$F_{35}(1930)$ are found to be essential in the range of 1.6 - 1.8 GeV. The\nrecent beam asymmetry data of Compton scattering from the GRAAL facility are\nused to determine the helicity couplings of these resonances, and strong\nconstraints are coming also from $\\pi N$ and $K\\Sigma$ photoproduction data.\nThe possible spin and parity of new narrow resonances is discussed.", "category": "nucl-th" }, { "text": "Influence of non-statistical properties in nuclear structure on emission\n of prompt fission neutrons: The Hauser-Feshbach Fission Fragment Decay (HF$^3$D) model is extended to\ncalculate the prompt fission neutron spectrum (PFNS) for the thermal neutron\ninduced fission on $^{235}$U, where the evaporated neutrons from all possible\nfission fragment pairs are aggregated. By studying model parameter\nsensitivities on the calculated PFNS, as well as non-statistical behavior of\nlow-lying discrete level spin distribution, we conclude that discrepancies\nbetween the aggregation calculation and the experimental PFNS seen at higher\nneutron emission energies can be attributed to both the primary fission\nfragment yield distribution and the possible high spin states that are not\npredicted by the statistical theory of nuclear structure.", "category": "nucl-th" }, { "text": "Intrinsic operators for the electromagnetic nuclear current: The intrinsic electromagnetic nuclear meson exchange charge and current\noperators arising from a separation of the center-of-mass motion are derived\nfor a one-boson-exchange model for the nuclear interaction with scalar,\npseudoscalar and vector meson exchange including leading order relativistic\nterms. Explicit expressions for the meson exchange operators corresponding to\nthe different meson types are given in detail for a two-nucleon system. These\nintrinsic operators are to be evaluated between intrinsic wave functions in\ntheir center-of-mass frame.", "category": "nucl-th" }, { "text": "Three-body resonances Lambda-n-n and Lambda-Lambda-n: Possible bound and resonant states of the hypernuclear systems $\\Lambda nn$\nand $\\Lambda\\Lambda n$ are sought as zeros of the corresponding three-body Jost\nfunctions calculated within the framework of the hyperspherical approach with\nlocal two-body S-wave potentials describing the $nn$, $\\Lambda n$, and\n$\\Lambda\\Lambda$ interactions. Very wide near-threshold resonances are found\nfor both three-body systems. The positions of these resonances turned out to be\nsensitive to the choice of the $\\Lambda n$-potential. Bound $\\Lambda nn$ and\n$\\Lambda\\Lambda n$ states only appear if the two-body potentials are multiplied\nby a factor of $\\sim 1.5$.", "category": "nucl-th" }, { "text": "Dense nuclear matter and symmetry energy in strong magnetic fields: The properties of nuclear matter in the presence of a strong magnetic field,\nincluding the density-dependent symmetry energy, the chemical composition and\nspin polarizations, are investigated in the framework of the relativistic mean\nfield models FSU-Gold. The anomalous magnetic moments (AMM) of the particles\nand the nonlinear isoscalar-isovector coupling are included. It is found that\nthe parabolic isospin-dependence of the energy per nucleon of asymmetric\nnuclear matter remains valid for values of the magnetic field below\n$10^{5}B_{c}^{e}$, $B_{c}^{e}=4.414\\times10^{13}$G being the electron critical\nfield. Accordingly, the symmetry energy can be obtained by the difference of\nthe energy per nucleon in pure neutron matter and that in symmetric matter. The\nsymmetry energy, which is enhanced by the presence of the magnetic field,\nsignificantly affects the chemical composition and the proton polarization. The\neffects of the AMM of each component on the energy per nucleon, symmetry\nenergy, chemical composition and spin polarization are discussed in detail.", "category": "nucl-th" }, { "text": "Magicity of the $^{52}$Ca and $^{54}$Ca isotopes and tensor contribution\n within a mean--field approach: We investigate the magicity of the isotopes $^{52}$Ca and $^{54}$Ca, that was\nrecently confirmed by two experimental measurements, and relate it to\nlike--particle and neutron--proton tensor effects within a mean--field\ndescription. By analyzing Ca isotopes, we show that the like--particle tensor\ncontribution induces shell effects that render these nuclei more magic than\nthey would be predicted by neglecting it. In particular, such induced shell\neffects are stronger in the nucleus $^{52}$Ca and the single--particle gaps are\nincreased in both isotopes due to the tensor force. By studying $N=32$ and\n$N=34$ isotones, neutron--proton tensor effects may be isolated and their role\nanalyzed. It is shown that neutron--proton tensor effects lead to increasing\n$N=32$ and $N=34$ gaps, when going along isotonic chains, from $^{58}$Fe to\n$^{52}$Ca, and from $^{60}$Fe to $^{54}$Ca, respectively.\n The mean--field calculations are perfomed by employing one Skyrme parameter\nset, that was introduced in a previous work by fitting the tensor parameters\ntogether with the spin--orbit strength. The signs and the values of the tensor\nstrengths are thus checked within this specific application. The obtained\nresults indicate that the employed parameter set, even if generated with a\npartial adjustment of the parameters of the force, leads to the correct shell\nbehavior and provides, in particular, a description of the magicity of\n$^{52}$Ca and $^{54}$Ca within a pure mean--field picture with the effective\ntwo--body Skyrme interaction.", "category": "nucl-th" }, { "text": "The 3D structure of anisotropic flow in small collision systems at the\n Relativistic Heavy Ion Collider: We present (3+1)D dynamical simulations of asymmetric nuclear collisions at\nthe Relativistic Heavy Ion Collider (RHIC). Employing a dynamical initial state\nmodel coupled to (3+1)D viscous relativistic hydrodynamics, we explore the\nrapidity dependence of anisotropic flow in the RHIC small system scan at 200\nGeV center of mass energy. We calibrate parameters to describe central\n$^3$He+Au collisions and make extrapolations to d+Au and p+Au collisions. Our\ncalculations demonstrate that approximately 50% of the $v_3(p_T)$ difference\nbetween the measurements by the STAR and PHENIX Collaborations can be explained\nby the use of reference flow vectors from different rapidity regions. This\nemphasizes the importance of longitudinal flow decorrelation for anisotropic\nflow measurements in asymmetric nuclear collisions, and the need for (3+1)D\nsimulations. We also present results for the beam energy dependence of particle\nspectra and anisotropic flow in d+Au collisions.", "category": "nucl-th" }, { "text": "Four-body structure of neutron-rich hypernucleus $^6_\u039b$H: The structure of heavy hyperhydrogen $^6_{\\Lambda}$H is studied within the\nframework of a $tnn\\Lambda$ four-body cluster model. Interactions among the\nconstituent subunits are determined so as to reproduce reasonably well the\nobserved low-energy properties of the $tn, t\\Lambda$ and $tnn$ subsystems. As\nlong as we reproduce the energy and width of $^5$H within the error bar, the\nground state of $^6_{\\Lambda}$H is obtained as a resonant state.", "category": "nucl-th" }, { "text": "Formation of Few-Body Clusters in Nuclear Matter: Starting from a suitably modified three-body equation to include dominant\nmedium effects such as self energy corrections and Pauli blocking I present\nresults on several observables relevant for the formation of light clusters in\na heavy ion collision at moderate energies. Properly taking into account the\nmedium leads to the Mott effect, larger reaction rates, in turn, faster time\nscales for the deuteron life time and chemical relaxation time. Within a\nBoltzmann-Uehling-Uhlenbeck approach to simulate the heavy ion reactions, also\nthe total number of deuterons and the energy spectrum are significantly changed\ndue to medium effects in the elementary cross sections entering into the\ncollision integrals.", "category": "nucl-th" }, { "text": "Thermal Properties of Asymmetric Nuclear Matter: The thermal properties of asymmetric nuclear matter are investigated in a\nrelativistic mean- field approach. We start from free space NN-interactions and\nderive in-medium self-energies by Dirac-Brueckner theory. By the DDRH procedure\nwe derive in a self-consistent approach density- dependent meson-baryon\nvertices. At the mean-field level, we include isoscalar and isovector scalar\nand vector interactions. The nuclear equation of state is investigated for a\nlarge range of total baryon densities up to the neutron star regime, the full\nrange of asymmetries from symmetric nuclear matter to pure neutron matter, and\ntemperatures up to T~100 MeV. The isovector-scalar self-energies are found to\nmodify strongly the thermal properties of asymmetric nuclear matter. A striking\nresult is the change of phase transitions when isovector-scalar self-energies\nare included.", "category": "nucl-th" }, { "text": "Modification of magicity towards the dripline and its impact on\n electron-capture rates for stellar core-collapse: The importance of microphysical inputs from laboratory nuclear experiments\nand theoretical nuclear structure calculations in the understanding of the core\ncollapse dynamics, and the subsequent supernova explosion, is largely\nrecognized in the recent literature. In this work, we analyze the impact of the\nmasses of very neutron rich nuclei on the matter composition during collapse,\nand the corresponding electron capture rate. To this aim, we introduce an\nempirical modification of the popular Duflo-Zuker mass model to account for\npossible shell quenching far from stability, and study the effect of the\nquenching on the average electron capture rate. We show that the preeminence of\nthe $N=50$ and $N=82$ closed shells in the collapse dynamics is considerably\ndecreased if the shell gaps are reduced in the region of $^{78}$Ni and beyond.\nAs a consequence, local modifications of the overall electron capture rate up\nto 30\\% can be expected, with integrated values strongly dependent on the\nstiffness of magicity quenching and progenitor mass and potential important\nconsequences on the entropy generation, the neutrino emissivity, and the mass\nof the core at bounce. Our work underlines the importance of new experimental\nmeasurements in this region of the nuclear chart, the most crucial information\nbeing the nuclear mass and the Gamow-Teller strength. Reliable microscopic\ncalculations of the associated elementary rate, in a wide range of temperatures\nand electron densities, optimized on these new empirical information, will be\nadditionally needed to get quantitative predictions of the collapse dynamics.", "category": "nucl-th" }, { "text": "The Nuclear Shell Model Toward the Drip Lines: We describe the \"islands of inversion\" that occur when approaching the\nneutron drip line around the magic numbers N=20, N=28 and N=40 in the framework\nof the Interacting Shell Model in very large valence spaces. We explain these\nconfiguration inversions (and the associated shape transitions) as the result\nof the competition between the spherical mean field (monopole) which favors\nmagicity and the correlations (multipole) which favor deformed intruder states.\nWe also show that the N=20 and N=28 islands are in reallity a single one, which\nfor the Magnesium isotopes is limited by N=18 and N=32.", "category": "nucl-th" }, { "text": "Isospin breaking in the reaction np --> dpi^0 at threshold: The model for charge symmetry breaking in the reaction np --> dpi^0 applied\nearlier around the Delta region is used to calculate the integrated\nforward-backward asymmetry of the cross section close to threshold. The mixing\nof the pi and eta mesons appears as strongly dominant at these energies. This\ncontrasts elastic np scattering experiments, where the np mass difference in\nOPE dominates, or np --> d\\pi^0 closer to the Delta region.", "category": "nucl-th" }, { "text": "Invariant amplitudes for coherent electromagnetic pseudoscalar\n production from a spin-one target (II): crossing, multipoles and observables: The formal properties of the recently derived set of linearly independent\ninvariant amplitudes for the electromagnetic production of a pseudoscalar\nparticle from a spin-one particle have been further exploited. The crossing\nproperties are discussed in detail. Since not all of the amplitudes have simple\ncrossing behaviour, we introduce an alternative set of basic amplitudes which\nare either symmetric or antisymmetric under crossing. The multipole\ndecomposition is given, and the representation of the multipoles as integrals\nover the invariant functions weighted with Legendre polynomials is derived.\nFurthermore, differential cross section and polarization observables are\nexpressed in terms of the corresponding invariant functions.", "category": "nucl-th" }, { "text": "Meson Condensation in Dense Matter Revisited: The results for meson condensation in the literature vary markedly depending\non whether one uses chiral perturbation theory or the current-algebra-plus-PCAC\napproach. To elucidate the origin of this discrepancy, we re-examine the role\nof the sigma-term in meson condensation. We find that the resolution of the\nexisting discrepancy requires a knowledge of terms in the Lagrangian that are\nhigher order in density than hitherto considered.", "category": "nucl-th" }, { "text": "Using Continuum Level Density in the Pairing Hamiltonian: BCS and Exact\n Solutions: Pairing plays a central role in nuclear systems. The simplest model for the\npairing is the constant-pairing Hamiltonian. The aim of the present paper is to\ninclude the continuum single particle level density in the constant pairing\nHamiltonian and to make a comparison between the approximate BCS and the exact\nRichardson solutions. The continuum is introduced by using the continuum single\nparticle level density. It is shown that the continuum makes an important\ncontribution to the pairing parameter even in those case when the continuum is\nweakly populated. It is shown that while the approximate BCS solution depends\non the model space the exact Richardson solution does not.", "category": "nucl-th" }, { "text": "Diabatic Mean-Field Description of Rotational Bands in Terms of the\n Selfconsistent Collective Coordinate Method: Diabatic description of rotational bands provides a clear-cut picture for\nunderstanding the back-bending phenomena, where the internal structure of the\nyrast band changes dramatically as a function of angular momentum. A\nmicroscopic framework to obtain the diabatic bands within the mean-field\napproximation is presented by making use of the selfconsistent collective\ncoordinate method. Applying the framework, both the ground state rotational\nbands and the Stockholm bands are studied systematically for the rare-earth\ndeformed nuclei. An overall agreement has been achieved between the calculated\nand observed rotational spectra. It is also shown that the inclusion of the\ndouble-stretched quadrupole-pairing interaction is crucial to obtain an overall\nagreement for the even-odd mass differences and the rotational spectra\nsimultaneously.", "category": "nucl-th" }, { "text": "Aspects of meson properties in dense nuclear matter: We investigate the modification of meson spectral densities in dense nuclear\nmatter at zero temperature. These effects are studied in a fully relativistic\nmean field model which goes beyond the linear density approximation and also\nincludes baryon resonances. In particular, the role of N*(1520) and N*(1720) on\nthe rho meson spectral density is highlighted. Even though the nucleon-nucleon\nloop and the nucleon-resonance loop contribute with the opposite sign, an\noverall reduction of rho meson mass is still observed at high density.\nImportantly, it is shown that the resonances cause substantial broadening of\nthe rho meson spectral density in matter and also induces non-trivial momentum\ndependence. The spectral density of the a0 meson is also shown. We study the\ndispersion relations and collective oscillations induced by the rho meson\npropagation in nuclear matter together with the influence of the mixing of rho\nwith the a0 meson. The relevant expression for the plasma frequency is also\nrecovered analytically in the appropriate limit.", "category": "nucl-th" }, { "text": "Quantum Monte Carlo calculations of magnetic moments and M1 transitions\n in $A \\le 9$ nuclei: We present Quantum Monte Carlo calculations of magnetic moments and M1\ntransitions in $A\\le 9$ nuclei which take into account contributions of\ntwo-body electromagnetic currents. The Hamiltonian utilized to generate the\nnuclear wave functions includes the realistic Argonne-{\\it v}$_{18}$\ntwo-nucleon and the Illinois-7 three-nucleon interactions. The nuclear two-body\nelectromagnetic currents are derived from a pionful chiral effective field\ntheory including up to one-loop corrections. These currents involve unknown Low\nEnergy Constants which have been fixed so as to reproduce a number of\nexperimental data for the two- and three-nucleon systems, such as $np$ phase\nshifts and deuteron, triton, and $^3$He magnetic moments. This preliminary\nstudy shows that two-body contributions provide significant corrections which\nare crucial to bring the theory in agreement with the experimental data in both\nmagnetic moments and M1 transitions.", "category": "nucl-th" }, { "text": "Deformation effect on nuclear density profile and radius enhancement in\n light- and medium-mass neutron-rich nuclei: Mass number dependence of the nuclear radii is closely related to the nuclear\nmatter properties. It is known that the most of nuclei exhibit some\ndeformation. We discuss how the nuclear density profile is modified by the\nnuclear deformation to elucidate the enhancement mechanism of the nuclear radii\nthrough a systematic investigation of neutron-rich Ne, Mg, Si, S, Ar, Ti, Cr,\nand Fe isotopes. Skyrme-Hartree-Fock calculations are performed in a\nthree-dimensional Cartesian grid to describe the nuclear deformation in a\nnon-empirical way. The role of the nuclear deformation on the nuclear density\nprofiles is explored in comparison to calculations with spherical limit. We\nfind correlations between the nuclear deformation and the internal nuclear\ndensity. The evolution of the nuclear radii appears to follow the core swelling\nmechanism recently proposed in spherical nuclei [Phys. Rev. C 101, 061301(R)\n(2020)], and the radius is further enhanced by the nuclear deformation. This\nstudy demands further theoretical and experimental investigations for the\ninternal density.", "category": "nucl-th" }, { "text": "Ground state energy fluctuations in the Nuclear Shell Model: Statistical fluctuations of the nuclear ground state energies are estimated\nusing shell model calculations in which particles in the valence shells\ninteract through well defined forces, and are coupled to an upper shell\ngoverned by random 2-body interactions. Induced ground-state energy\nfluctuations are found to be one order of magnitude smaller than those\npreviously associated with chaotic components, in close agreement with\nindependent perturbative estimates based on the spreading widths of excited\nstates.", "category": "nucl-th" }, { "text": "Symplectic No-core Shell-model Approach to Intermediate-mass Nuclei: We present a microscopic description of nuclei in an intermediate-mass\nregion, including the proximity to the proton drip line, based on a no-core\nshell model with a schematic many-nucleon long-range interaction with no\nparameter adjustments. The outcome confirms the essential role played by the\nsymplectic symmetry to inform the interaction and the winnowing of shell-model\nspaces. We show that it is imperative that model spaces be expanded well beyond\nthe current limits up through fifteen major shells to accommodate particle\nexcitations that appear critical to highly-deformed spatial structures and the\nconvergence of associated observables.", "category": "nucl-th" }, { "text": "J/psi production in relativistic heavy ion collisions from a multi-phase\n transport model: Using A Multi-Phase Transport (AMPT) model, we study J/psi production from\ninteractions between charm and anti-charm quarks in initial parton phase and\nbetween D and Dbar mesons in final hadron phase of relativistic heavy ion\ncollisions at the Relativistic Heavy Ion Collider (RHIC). Including also the\ninverse reactions of J/psi absorption by gluons and light mesons, we find that\nthe net number of J/psi from the parton and hadron phases is smaller than that\nexpected from the superposition of initial nucleon-nucleon collisions, contrary\nto the J/psi enhancement predicted by the kinetic formation model. The\nproduction of J/psi is further suppressed if one includes the color screening\neffect in the parton phase. We have also studied the dependence of J/psi\nproduction on the charm quark mass and the effective charm meson mass.", "category": "nucl-th" }, { "text": "Parity-Violating Interaction Effects I: the Longitudinal Asymmetry in pp\n Elastic Scattering: The proton-proton parity-violating longitudinal asymmetry is calculated in\nthe lab-energy range 0--350 MeV, using a number of different, latest-generation\nstrong-interaction potentials--Argonne V18, Bonn-2000, and Nijmegen-I--in\ncombination with a weak-interaction potential consisting of rho- and\nomega-meson exchanges--the model known as DDH. The complete scattering problem\nin the presence of parity-conserving, including Coulomb, and parity-violating\npotentials is solved in both configuration- and momentum-space. The predicted\nparity-violating asymmetries are found to be only weakly dependent upon the\ninput strong-interaction potential adopted in the calculation. Values for the\nrho- and omega-meson weak coupling constants $h^{pp}_\\rho$ and $h^{pp}_\\omega$\nare determined by reproducing the measured asymmetries at 13.6 MeV, 45 MeV, and\n221 MeV.", "category": "nucl-th" }, { "text": "Spin-isospin response of deformed neutron-rich nuclei in a\n self-consistent Skyrme energy-density-functional approach: We develop a new framework of the self-consistent deformed proton-neutron\nquasiparticle-random-phase approximation (pnQRPA), formulated in the\nHartree-Fock-Bogoliubov (HFB) single-quasiparticle basis. The same Skyrme force\nis used in both the HFB and pnQRPA calculations except in the proton-neutron\nparticle-particle channel, where an S=1 contact force is employed. Numerical\napplication is performed for Gamow-Teller (GT) strength distributions and\n$\\beta$-decay rates in the deformed neutron-rich Zr isotopes located around the\npath of the rapid-neutron-capture process nucleosynthesis. It is found that the\nGT strength distributions are fragmented due to deformation. Furthermore we\nfind that the momentum-dependent terms in the particle-hole residual\ninteraction leads to a stronger collectivity of the GT giant resonance. The T=0\npairing enhances the low-lying strengths cooperatively with the T=1 pairing\ncorrelation, which shortens the $\\beta$-decay half lives by at most an order of\nmagnitude. The new calculation scheme reproduces well the observed isotopic\ndependence of the $\\beta$-decay half lives of deformed $^{100-110}$Zr isotopes.", "category": "nucl-th" }, { "text": "Role of baryon resonances in the $\u03c0^-p \\to ne^+e^-$ reaction within an\n effective-Lagrangian model: We present a study of the reaction $\\pi^-p \\to ne^+e^-$ for\n$\\sqrt{s}=1.49\\,\\textrm{GeV}$, including non-resonant Born terms and\ncontributions of the $N(1440)$, $N(1520)$, $N(1535)$ resonances ($R$), using an\neffective-Lagrangian model, which we extended by a phenomenological phase\nfactor at the $RN\\rho$ vertex function. We give predictions for both the\ndifferential cross section $d\\sigma/dm$ and the spin density matrix elements of\nthe virtual photon that decays into the lepton pair. In the studied energy\nrange, the cross section is dominated by the Born and $N(1520)$ contributions.", "category": "nucl-th" }, { "text": "A Hartree-Bose Mean-Field Approximation for IBM-3: A Hartree-Bose mean-field approximation for the IBM-3 is presented. A\nHartree- Bose transformation from spherical to deformed bosons with\ncharge-dependent parameters is proposed which allows bosonic pair correlations\nand includes higher angular momentum bosons. The formalism contains previously\nproposed IBM-2 and IBM-3 intrinsic states as particular limits.", "category": "nucl-th" }, { "text": "Neutrino-induced single-pion production: Kinematics and Cross Section: In the energy range of present and future accelerator-based\nneutrino-oscillation experiments, single-pion production (SPP) is one of the\nmain contributions to the neutrino-nucleus scattering cross section. For these\nneutrino energies, ranging from several hundreds of MeV to a few GeV, the SPP\non the nucleus is usually described by the reaction in which the incoming\nlepton couples to one bound nucleon in the nucleus, producing a pion and the\nknock-out nucleon, along with the residual system and the scattered lepton in\nthe final state. Here, the kinematics and cross section formula for this\nprocess are discussed, although the formalism can be applied to other\n$2\\rightarrow4$ processes.", "category": "nucl-th" }, { "text": "Isovector properties of quark matter and quark stars in an\n isospin-dependent confining model: The confining quark matter (CQM) model, in which the confinement and\nasymptotic freedom are modeled via the Richardson potential for quark-quark\nvector interaction and the chiral symmetry restoration at high density is\ndescribed by the density dependent quark mass, is extended to include isospin\ndependence of the quark mass. Within this extended isospin-dependent confining\nquark matter (ICQM) model, we study the properties of strange quark matter and\nquark stars. We find that including isospin dependence of the quark mass can\nsignificantly influence the quark matter symmetry energy, the stability of\nstrange quark matter and the mass-radius relation of quark stars. In\nparticular, we demonstrate although the recently discovered large mass pulsars\nPSR J1614.2230 and PSR J0348+0432 with masses around two times solar mass\n($2M_{\\odot}$) cannot be quark stars within the original CQM model, they can be\nwell described by quark stars in the ICQM model if the isospin dependence of\nquark mass is strong enough so that the quark matter symmetry energy is about\nfour times that of a free quark gas. We also discuss the effects of the density\ndependence of quark mass on the properties of quark stars. Our results indicate\nthat the heavy quark stars with mass around $2M_{\\odot}$ (if exist) can put\nstrong constraints on isospin and density dependence of the quark mass as well\nas the quark matter symmetry energy.", "category": "nucl-th" }, { "text": "Rearrangement in folding potentials with density-dependent\n nucleon-nucleon interaction: We discuss optical potentials for the nuclear elastic scattering from a\nvariational viewpoint.\n Density-dependence in the effective $N$-$N$ interaction leads to density\nrearrangement terms, in addition to the conventional folding term.\n Effects of the rearrangement on the $N$-$A$ optical potential are illustrated\nin the nuclear-matter limit.\n Closely relating to consistency with the saturation, the rearrangement\nappreciably improves the isoscalar optical potential depth over the previous\nfolding model calculations.\n The rearrangement gives stronger effects as the density grows.\n We also present rearrangement terms in the $A$-$A$ double-folding potential.\n Since the rearrangement terms are relevant to the nuclear structure but\nshould be handled within the reaction model,\n $N$-$N$ effective interactions applicable both to structure models and to the\nfolding model will be desired for unambiguous description of the nuclear\nelastic scattering.", "category": "nucl-th" }, { "text": "No-Core shell model for A = 47 and A = 49: We apply an {\\it ab-initio} approach to the nuclear structure of odd-mass\nnuclei straddling $^{48}Ca$. Starting with the NN interaction, that fits\ntwo-body scattering and bound state data we evaluate the nuclear properties of\n$A = 47$ and $A = 49$ nuclei in a no-core approach. Due to model space\nlimitations and the absence of 3-body interactions, we incorporate\nphenomenological terms determined by fits to $A = 48$ nuclei in a previous\neffort. Our modified Hamiltonian produces reasonable spectra for these odd mass\nnuclei. In addition to the differences in single-particle basis states, the\nabsence of a single-particle Hamiltonian in our no-core approach obscures\ndirect comparisons with valence effective NN interactions. Nevertheless, we\ncompare the fp-shell matrix elements of our initial and modified Hamiltonians\nin the harmonic oscillator basis with a recent model fp-shell interaction, the\nGXPF1 interaction of Honma, Otsuka, Brown and Mizusaki. Notable differences\nemerge from these comparisons. In particular, our diagonal two-body $T = 0$\nmatrix elements are, on average, about 800-900keV more attractive. Furthermore,\nwhile our initial and modified NN Hamiltonian fp-shell matrix elements are\nstrongly correlated, there is much less correlation with the GXPF1 matrix\nelements.", "category": "nucl-th" }, { "text": "Molecule model for kaonic nuclear cluster anti-KNN: We analyse the properties of the kaonic nuclear cluster (KNC) anti-KNN with\nthe structure Nx(anti-KN)_(I = 0), having the quantum numbers I(J^P) =\n1/2(0^-), and treated as a quasi-bound hadronic molecule state. We describe the\nproperties of the hadronic molecule, or the KNC Nx(anti-KN)_(I = 0), in terms\nof vibrational degrees of freedom with oscillator wave functions and chiral\ndynamics. These wave functions, having the meaning of trial wave functions of\nvariational calculations, are parameterised by the frequency of oscillations of\nthe (anti-KN)_(I = 0) pair, which is fixed in terms of the binding energy of\nthe strange baryon resonance Lambda(1405), treated as a quasi-bound\n(anti-KN)_(I = 0) state. The binding energies B_X and widths Gamma_X of the\nstates X = (anti-KN)_(I = 0) and X = anti-KNN, respectively, are calculated in\nthe heavy-baryon approximation by using chiral Lagrangians with meson-baryon\nderivative couplings invariant under chiral SU(3)xSU(3) symmetry at the\ntree-level approximation. The results are B_(anti-KNN) = 40.2 MeV and\nGamma_(anti-KNN) = Gamma^(non-pionic)_(anti-KNN) + Gamma^(pionic)_(anti-KNN) ~\n(85 - 106) MeV and, where Gamma^(non-pionic)_(anti-KNN) ~ 21 MeV and\nGamma^(pionic)_(anti-KNN) ~ (64 - 86) MeV are the widths of non-pionic anti-KNN\n-> N Lambda^0, N Sigma and pionic anti-KNN -> N Sigma pi decay modes,\ncalculated for B_(anti-KN) = 29 MeV and Gamma_(anti-KN) = (30 - 40) MeV,\nrespectively.", "category": "nucl-th" }, { "text": "Jet-medium interaction and conformal relativistic fluid dynamics: A formalism to study the mode-by-mode response to the energy deposition of\nexternal hard partons propagating in a relativistic fluid is developed, based\non a semi-analytical solution of conformal fluid-dynamics. The soft particle\nproduction resulting from the jet-medium interaction is calculated and the\nrecoil of the viscous medium is studied for different orientations of the\nrelativistic jets, and for different values of the specific shear viscosity\n$\\eta/s$.", "category": "nucl-th" }, { "text": "Correlations in ultra-relativistic nuclear collisions with strings: While string models describe initial state radiation in ultra-relativistic\nnuclear collisions well, they mainly differ in their end-point positions of the\nstrings in spatial rapidity. We present a generic model where wounded\nconstituents are amended with strings whose both end-point positions fluctuate\nand analyze semi-analytically various scenarios of string-end-point\nfluctuations. In particular we constrain the different cases to experimental\ndata on rapidity spectra from collisions at $\\sqrt{s_{\\rm NN}}=200$~GeV, and\nexplore their respective two-body correlations, which allows to partially\ndiscriminate the possible solutions.", "category": "nucl-th" }, { "text": "Confronting a set of Skyrme and $\u03c7_{EFT}$ predictions for the crust\n of neutron stars: With the improved accuracy of neutron star observational data, it is\nnecessary to derive new equation of state where the crust and the core are\nconsistently calculated within a unified approach. For this purpose we describe\nnon-uniform matter in the crust of neutron stars employing a compressible\nliquid-drop model, where the bulk and the neutron fluid terms are given from\nthe same model as the one describing uniform matter present in the core. We\nthen generate a set of fifteen unified equations of state for cold catalyzed\nneutron stars built on realistic modelings of the nuclear interaction, which\nbelongs to two main groups: the first one derives from the phenomenological\nSkyrme interaction and the second one from $\\chi_{EFT}$ Hamiltonians. The\nconfrontation of these model predictions allows us to investigate the model\ndependence for the crust properties, and in particular the effect of neutron\nmatter at low density. The new set of unified equations of state is available\nat the CompOSE repository.", "category": "nucl-th" }, { "text": "Multiplicity Fluctuations in Nucleus-Nucleus Collisions: Dependence on\n Energy and Atomic Number: Event-by-event multiplicity fluctuations in central C+C, S+S, In+In, and\nPb+Pb as well as p+p collisions at bombarding energies from 10 to 160 AGeV are\nstudied within the HSD and UrQMD microscopic transport approaches. Our\ninvestigation is directly related to the future experimental program of the\nNA61 Collaboration at the SPS for a search of the QCD critical point. The\ndependence on energy and atomic mass number of the scaled variances for\nnegative, positive, and all charged hadrons is presented and compared to the\nresults of the model of independent sources. Furthermore, the nucleus-nucleus\nresults from the transport calculations are compared to inelastic proton-proton\ncollisions for reference. We find a dominant role of the participant number\nfluctuations in nucleus-nucleus reactions at finite impact parameter $b$. In\norder to reduce the influence of the participant numbers fluctuations on the\ncharged particle multiplicity fluctuations only the most central events have to\nbe selected. Accordingly, the samples of the 1% most central nucleus-nucleus\ncollisions with the largest numbers of the projectile participants are studied.\nThe results are compared with those for collisions at zero impact parameter. A\nstrong influence of the centrality selection criteria on the multiplicity\nfluctuations is pointed out. Our findings are essential for an optimal choice\nof colliding nuclei and bombarding energies for the experimental search of the\nQCD critical point.", "category": "nucl-th" }, { "text": "The black hole spin influence on accretion disk neutrino detection: Neutrinos are copiously emitted from black hole accretion disks playing a\nfundamental role in their evolution, as well as in the production of gamma ray\nbursts and r-process nucleosynthesis. The black hole generates a strong\ngravitational field able to change the properties of the emerging neutrinos. We\nstudy the influence of the black hole spin on the structure of the neutrino\nsurfaces, neutrino luminosities, average neutrino energies, and event counts at\nSuperK. We consider several disk models and provide estimates that cover\ndifferent black hole efficiency scenarios. We discuss the influence of the\ndetector's inclination with respect to the axis of the torus on neutrino\nproperties. We find that tori around spinning black holes have larger\nluminosities, energies and rates compared to tori around static black holes,\nand that the inclination of the observer causes a reduction in the luminosities\nand detection rates but an increase in the average energies.", "category": "nucl-th" }, { "text": "Nuclear transparency in quasielastic A(e,e'p): intranuclear cascade\n versus eikonal approximation: The problem of nuclear propagation through the nuclear medium in quasielastic\nA(e,e'p) reactions is discussed in the kinematic range 1eta,N branching ratio of (0.15 +0.35 -0.10)%.", "category": "nucl-th" }, { "text": "Ab initio many-body calculations of nucleon-nucleus scattering: We develop a new ab initio many-body approach capable of describing\nsimultaneously both bound and scattering states in light nuclei, by combining\nthe resonating-group method with the use of realistic interactions, and a\nmicroscopic and consistent description of the nucleon clusters. This approach\npreserves translational symmetry and Pauli principle. We outline technical\ndetails and present phase shift results for neutron scattering on 3H, 4He and\n10Be and proton scattering on 3He and 4He, using realistic nucleon-nucleon (NN)\npotentials. Our A=4 scattering results are compared to earlier ab initio\ncalculations. We find that the CD-Bonn NN potential in particular provides an\nexcellent description of nucleon-4He S-wave phase shifts. On the contrary, the\nexperimental nucleon-4He P-wave phase shifts are not well reproduced by any NN\npotential we use. We demonstrate that a proper treatment of the coupling to the\nn-10Be continuum is successful in explaining the parity-inverted ground state\nin 11Be.", "category": "nucl-th" }, { "text": "The neutron distribution in nuclei as measured with parity violating\n electron scattering: A short review of the present knowledge of the nucleons distribution in\nnuclei is given. A proposal is made about a possible measurements of the\nneutron distribution through polarized electron scattering off nuclei.", "category": "nucl-th" }, { "text": "Neutrino-Neutron Scattering Opacities in Supernova Matter: We compute the static density and spin structure factors in the long\nwavelength limit for pure neutron matter at subsaturation densities relevant to\ncore-collapse supernovae within the Brueckner-Hartree-Fock (BHF) approach. The\nBHF results are reliable at high densities, extending beyond the validity of\nthe virial expansion. Motivated by the similarities between the dilute neutron\ngas and a unitary gas, we propose a phenomenological approach to derive the\nstatic structures with finite momentum transfer as well as the dynamic ones\nwith simple analytical expressions, based on the computed static structures in\nthe long wavelength limit. We also compare the in-medium neutrino-neutron\nscattering cross sections using different structure factors. Our study\nemphasizes the importance of accurately computing the static structure factors\ntheoretically and utilizing the full dynamic structure factors in core-collapse\nsupernova simulations.", "category": "nucl-th" }, { "text": "Relativistic second order dissipative hydrodynamics from effective\n fugacity quasi particle model: In this work a second order relativistic viscous hydrodynamic model has been\npresented based on the effective fugacity quasi-particle model (EQPM). The\nhydro model has been derived from the effective relativistic second-order\ntransport equation under EQPM for a multi-particle (two component) system and\nsolving it in Grad's 14 moment method. The EQPM model describes the strongly\ninteracting thermal system of QCD interactions through its fugacity parameters\nextracted from an updated lattice equations of state. The proper time evolution\nof temperature and pressure anisotropy is observed to be affected significantly\ndue to the inclusion of EQPM model compared to an ideal system.", "category": "nucl-th" }, { "text": "Flavor content of nucleon form factors in the space- and time-like\n region: I discuss a two-component model of nucleon form factors in which the external\nphoton couples both to an intrinsic three-quark structure and to a meson cloud\nvia vector-meson dominance, and present a simultaneous analysis of the\nelectromagnetic form factors of the nucleon in the space- and time-like regions\nas well as their strangeness content.", "category": "nucl-th" }, { "text": "Near-threshold pion production with radioactive beams at the Rare\n Isotope Accelerator: Using an isospin- and momentum-dependent transport model we study\nnear-threshold pion production in heavy-ion collisions induced by radioactive\nbeams at the planned Rare Isotope Accelerator (RIA). We revisit the question of\nprobing the high density behavior of nuclear symmetry energy $E_{sym}(\\rho)$\nusing the $\\pi^-/\\pi^+$ ratio. It is found that both the total and differential\n$\\pi^-/\\pi^+$ ratios remain sensitive to the $E_{sym}(\\rho)$ when the\nmomentum-dependence of both the isoscalar and isovector potentials are\nconsistently taken into account. Moreover, the multiplicity and spectrum of\n$\\pi^-$ mesons are found more sensitive to the $E_{sym}(\\rho)$ than those of\n$\\pi^+$ mesons. Finally, effects of the Coulomb potential on the pion spectra\nand $\\pi^-/\\pi^+$ ratio are also discussed.", "category": "nucl-th" }, { "text": "Shell-model description of monopole shift in neutron-rich Cu: Variations in the nuclear mean-field, in neutron-rich nuclei, are\ninvestigated within the framework of the nuclear shell model. The change is\nidentified to originate mainly from the monopole part of the effective two-body\nproton-neutron interaction. Applications for the low-lying states in odd-$A$ Cu\nnuclei are presented. We compare the results using both schematic and realistic\nforces. We also compare the monopole shifts with the results obtained from\nlarge-scale shell-model calculations, using the same realistic interaction, in\norder to study two-body correlations beyond the proton mean-field variations.", "category": "nucl-th" }, { "text": "Parity Violation in Low-Energy np->d gamma and the Deuteron Anapole\n Moment: Parity violation in low-energy nuclear observables is included in the\npionless effective field theory. The model-independent relation between the\nparity-violating asymmetry in polarized np -> d gamma and the non-nucleon part\nof the deuteron anapole moment is discussed. The asymmetry in np -> d gamma\ncomputed with KSW power-counting, and recently criticized by Desplanques, is\ndiscussed.", "category": "nucl-th" }, { "text": "K$^+$-nucleus quasielastic scattering: K$^+$--nucleus quasielastic cross sections measured for a laboratory kaon\nbeam momentum of 705 MeV/$c$ are presented for 3--momentum transfers of 300 and\n500 MeV/$c$. The measured differential cross sections for C, Ca and Pb at 500\nMeV/$c$ are used to deduce the effective number of nucleons participating in\nthe scattering, which are compared with estimates based on the eikonal\napproximation. The long mean free path expected for K$^+$ mesons in nuclei is\nfound. Double differential cross sections for C and Ca are compared to\nrelativistic nuclear structure calculations.", "category": "nucl-th" }, { "text": "Deformed shell model results for neutrinoless double beta decay of\n nuclei in A=60-90 region: Nuclear transition matrix elements (NTME) for the neutrinoless double beta\ndecay of $^{70}$Zn, $^{80}$Se and $^{82}$Se nuclei are calculated within the\nframework of the deformed shell model based on Hartree-Fock states. For\n$^{70}$Zn, jj44b interaction in $^{2}p_{3/2}$, $^{1}f_{5/2}$, $^{2}p_{1/2}$ and\n$^{1}g_{9/2}$ space with $^{56}$Ni as the core is employed. However, for\n$^{80}$Se and $^{82}$Se nuclei, a modified Kuo interaction with the above core\nand model space are employed. Most of our calculations in this region were\nperformed with this effective interaction. However, jj44b interaction has been\nfound to be better for $^{70}$Zn. The above model space was used in many recent\nshell model and interacting boson model calculations for nuclei in this region.\nAfter ensuring that DSM gives good description of the spectroscopic properties\nof low-lying levels in these three nuclei considered, the NTME are calculated.\nThe deduced half-lives with these NTME, assuming neutrino mass is 1 eV, are\n$1.1 \\times 10^{26}$ yr, $2.3 \\times 10^{27}$ yr and $2.2 \\times 10^{24}$ yr\nfor $^{70}$Zn, $^{80}$Se and $^{82}$Se, respectively.", "category": "nucl-th" }, { "text": "The Onset of Color Transparency in $(e,e'p)$ Reactions on Nuclei: Quantum filtering of the ejectile wave packet from hard $ep$ scattering on\nbound nucleons puts stringent constraints on the onset of color transparency in\n$(e,e'p)$ reactions in nuclei at moderate energies. Based on\nmultiple-scattering theory, we derive a novel formula for nuclear transparency\nand discuss its energy dependence in terms of a color transparency sum rule.", "category": "nucl-th" }, { "text": "Weak sensitivity of three-body ($d,p$) reactions to $np$ force models: Adiabatic distorted-wave approximation (ADWA) study of three-body $(d,p)$\ntransfer reactions [G.W. Bailey, N.K. Timofeyuk, and J.A. Tostevin, Phys. Rev.\nLett. 117, 162502 (2016)] reported strong sensitivity of cross sections to the\nneutron-proton $(np)$ interaction model when the nucleon-nucleus optical\npotential is nonlocal. The verification of this unusual finding using more\nreliable methods is aimed for in the present work. A rigorous Faddeev-type\nthree-body scattering theory is applied to the study of $(d,p)$ transfer\nreactions. The equations for transition operators are solved in the\nmomentum-space partial-wave framework. Differential cross sections for\n$^{26}$Al$(d,p)^{27}$Al reactions are calculated using nonlocal nuclear optical\npotentials and a number of realistic $np$ potentials. Only a weak dependence on\nthe $np$ force model is observed, typically one order of magnitude lower than\nin the previous ADWA study. The shape of the angular distribution of the\nexperimental data is well reproduced. Cross sections of $(d,p)$ transfer\nreactions calculated using a rigorous three-body method show little sensitivity\nto the $np$ interaction model. This indicates a failure of the ADWA in the\ncontext of nonlocal potentials. Some evident shortcomings of the ADWA are\npointed out.", "category": "nucl-th" }, { "text": "Joint $R_{AA}$ and $v_2$ predictions for $Pb+Pb$ collisions at the LHC\n within DREENA-C framework: In this paper, we presented our recently developed DREENA-C framework, which\nis a fully optimized computational suppression procedure based on our\nstate-of-the-art dynamical energy loss formalism in constant temperature finite\nsize QCD medium. With this framework, we for the first time, generated joint\n$R_{AA}$ and $v_2$ predictions within our dynamical energy loss formalism. The\npredictions are generated for both light and heavy flavor probes, and different\ncentrality regions in $Pb+Pb$ collisions at the LHC, and compared with the\navailable experimental data. Despite the fact that DREENA-C does not contain\nmedium evolution (to which $v_2$ is largely sensitive) and the fact that other\napproaches faced difficulties in explaining $v_2$ data, we find that DREENA-C\nleads to qualitatively good agreement with this data, though quantitatively,\nthe predictions are visibly above the experimental data. Intuitive explanation\nbehind such results is presented, supporting the validity of our model, and it\nis expected that introduction of evolution in the ongoing improvement of DREENA\nframework, will lead to better joint agreement with $R_{AA}$ and $v_2$ data,\nand allow better understanding of the underlying QCD medium.", "category": "nucl-th" }, { "text": "Updating the nuclear reaction rate library REACLIB. (I. Experimental\n reaction rates of the proton-proton chain): REACLIB is one of the most comprehensive and popular astrophysical reaction\nrate libraries. However, its experimentally obtained rates for light isotopes\nstill rely mainly on the Caughlan & Fowler (1988) compilation and have never\nbeen updated despite the progress in many relevant nuclear astrophysics\nexperiments. Moreover, due to fitting errors REACLIB is not reliable at\ntemperatures lower than 10^{7}K. In this work we establish the formalism for\nupdating the obsolete Caughlan-Fowler experimental rates of REACLIB. Then we\nuse the NACRE compilation and results from the LUNA experiments to update some\nimportant charged-particle induced rates of REACLIB focusing on the\nproton-proton chain. The updated rates (available also in digital form) can now\nbe used in the low temperature regime (below 10^{7}K) which was forbidden to\nthe old version of REACLIB.", "category": "nucl-th" }, { "text": "Viscous Hydrodynamic Predictions for Nuclear Collisions at the LHC: Hydrodynamic simulations are used to make predictions for the integrated\nelliptic flow coefficient v_2 in sqrt(s)=5.5 TeV lead-lead and sqrt(s)=14 TeV\nproton-proton collisions at the LHC. We predict a 10% increase in v_2 from RHIC\nto Pb+Pb at LHC, and v_2 ~ 0 in p+p collisions unless eta/s < 0.08.", "category": "nucl-th" }, { "text": "Hadronisation in event generators from small to large systems: The results of the dynamical core-corona initialisation framework in p+p and\nPb+Pb collisions at the LHC energies are presented. We extract the fractions of\nfinal hadron yields originating from equilibrated and non-equilibrated matter\nas functions of multiplicity. We show that the contribution from\nnon-equilibrated matter is non-negligible even in intermediate and central\nPb+Pb collisions. The particle production from non-equilibrated matter behaves\nas a correction on $c_2\\{4\\}$ that is purely obtained from the equilibrated\nmatter. The result poses a warning on Bayesian parameter estimation with\nconventional hydrodynamic models. The observed flow coefficients might need a\nreinterpretation with new dynamical models which incorporate the particle\nproduction from non-equilibrated matter.", "category": "nucl-th" }, { "text": "Cumulants of conserved charges in hydrodynamic simulations: We introduce a fast and simple method of computing cumulants of net-proton or\nnet-charge fluctuations in event-by-event hydrodynamic simulations of heavy-ion\ncollisions. One evaluates the mean numbers of particles in every hydrodynamic\nevent. Cumulants are then expressed as a function of these mean numbers. We\nimplement the corrections due to global conservation laws. The method is tested\nusing ideal hydrodynamic simulations of Au+Au collisions at $\\sqrt{s_{NN}}=200$\nAGeV with the NeXSPheRIO code. Results are in good agreement with experimental\ndata on net-proton and net-charge fluctuations by the STAR collaboration.", "category": "nucl-th" }, { "text": "Three-Body Forces Produced by a Similarity Renormalization Group\n Transformation in a Simple Model: A simple class of unitary renormalization group transformations that force\nhamiltonians towards a band-diagonal form produce few-body interactions in\nwhich low- and high-energy states are decoupled, which can greatly simplify\nmany-body calculations. One such transformation has been applied to\nphenomenological and effective field theory nucleon-nucleon interactions with\nsuccess, but further progress requires consistent treatment of at least the\nthree-nucleon interaction. In this paper we demonstrate in an extremely simple\nmodel how these renormalization group transformations consistently evolve two-\nand three-body interactions towards band-diagonal form, and introduce a\ndiagrammatic approach that generalizes to the realistic nuclear problem.", "category": "nucl-th" }, { "text": "Solution to the Proton Radius Problem: The relationship between the electric form factors for the proton in the rest\nframe and in the Breit momentum frame is used to provide a value for the\ndifference in the mean squared charge radius of the proton evaluated in the two\nframes. Associating the muonic-hydrogen data analysis for the proton charge\nradius of 0.84087 fm with the rest frame and associating the electron\nscattering with the Breit frame yields a prediction 0f 0.87944 fm for the\nproton radius in the relativistic frame. The most recent value deduced via\nelectron scattering from the proton is 0.877(6)fm so that the frame dependence\nused here yields a plausible solution to the proton radius puzzle.", "category": "nucl-th" }, { "text": "A Nonlinear Realized Approach of SU(2) Chiral Symmetry Spontaneous\n Breaking and Properties of Nuclear Matter: A nonlinear realization of SU(2) chiral symmetry spontaneous breaking\napproach is developed in the composite operator formalism. A Lagrangian\nincluding quark, gluon and Goldstone boson degrees of freedom of the chiral\nquark model is obtained from the QCD Lagrangian. A way to link the chiral\nsymmetry spontaneous breaking formalism at hadron level and that at quark level\nis predicted. too. The application to nuclear matter shows that the approach is\nquite successful in describing the properties of nuclear matter and the quark\ncondensate in it.", "category": "nucl-th" }, { "text": "SPQR -- Spectroscopy: Prospects, Questions & Results: Tremendous progress has been made in mapping out the spectrum of hadrons over\nthe past decade with plans to make further advances in the decade ahead.\nBaryons and mesons, both expected and unexpected, have been found, the results\nof precision experiments often with polarized beams, polarized targets and\nsometimes polarization of the final states. All these hadrons generate poles in\nthe complex energy plane that are consequences of strong coupling QCD. They\nreveal how this works.", "category": "nucl-th" }, { "text": "Magnetic dipole excitation and its sum rule in nuclei with two valence\n nucleons: Background: Magnetic dipole (M1) excitation is the leading mode of nuclear\nexcitation by the magnetic field, which couples unnatural-parity states. Since\nthe M1 excitation occurs mainly for open-shell nuclei, the nuclear pairing\neffect is expected to play a role. As expected from the form of operator, this\nmode may provide the information on the spin-related properties, including the\nspin component of dineutron and diproton correlations. In general, the sum rule\nfor M1 transition strength has not been derived yet. Purpose: To investigate\nthe M1 excitation of the systems with two valence nucleons above the\nclosed-shell core, with pairing correlation included, and to establish the M1\nsum rule that could be used to validate theoretical and experimental\napproaches. Possibility to utilize the M1 excitation as a tool to investigate\nthe pairing correlation in medium is also discussed. Method: Three-body model,\nwhich consists of a rigid spherical core and two valence nucleons, is employed.\nInteractions for its two-body subsystems are phenomenologically determined in\norder to reproduce the two-body and three-body energies. We also derive the M1\nsum rule within this three-body picture. Conclusion: The introduced M1 sum rule\ncan be utilized as a benchmark for model calculations of M1 transitions in the\nsystems with two valence nucleons. The total sum of the M1 transition strength\nis related with the coupled spin of valence nucleons in the open shell, where\nthe pairing correlation is unnegligible. The three-body-model calculations for\n18 O, 18 Ne, and 42 Ca nuclei demonstrate a significant effect of the pairing\ncorrelations on the low-lying M1 transitions. Therefore, further experimental\nstudies of M1 transitions in those systems are on demand, in order to validate\nproposed sum rule, provide a suitable probe for the nuclear pairing in medium,\nas well as to optimize the pairing models.", "category": "nucl-th" }, { "text": "DREENA-A framework as a QGP tomography tool: We present a fully optimised framework DREENA-A based on a state-of-the-art\nenergy loss model. The framework can include any, in principle arbitrary,\ntemperature profile within the dynamical energy loss formalism. Thus, 'DREENA'\nstands for Dynamical Radiative and Elastic ENergy loss Approach, while 'A'\nstands for Adaptive. DREENA-A does not use fitting parameters within the energy\nloss model, allowing it to fully exploit differences in temperature profiles\nwhich are the only input in the framework. The framework applies to light and\nheavy flavor observables, different collision energies, and large and smaller\nsystems. This, together with the ability to systematically compare data and\npredictions within the same formalism and parameter set, makes DREENA-A a\nunique multipurpose QGP tomography tool.", "category": "nucl-th" }, { "text": "Nuclear vorticity in isoscalar E1 modes: Skyrme-RPA analysis: Two basic concepts of nuclear vorticity, hydrodynamical (HD) and\nRawenthall-Wambach (RW), are critically inspected. As a test case, we consider\nthe interplay of irrotational and vortical motion in isoscalar electric dipole\nE1(T=0) modes in $^{208}$Pb, namely the toroidal and compression modes. The\nmodes are described in a self-consistent random-phase-approximation (RPA) with\nthe Skyrme force SLy6. They are examined in terms of strength functions,\ntransition densities, current fields, and formfactors. It is shown that the RW\nconception (suggesting the upper component of the nuclear current as the\nvorticity indicator) is not robust. The HD vorticity is not easily applicable\neither because the definition of a velocity field is too involved in nuclear\nsystems. Instead, the vorticity is better characterized by the toroidal\nstrength which closely corresponds to HD treatment and is approximately\ndecoupled from the continuity equation.", "category": "nucl-th" }, { "text": "Relativistic third-order dissipative fluid dynamics from kinetic theory: We present the derivation of a novel third-order hydrodynamic evolution\nequation for shear stress tensor from kinetic theory. Boltzmann equation with\nrelaxation time approximation for the collision term is solved iteratively\nusing Chapman-Enskog like expansion to obtain the nonequilibrium phase-space\ndistribution function. Subsequently, the evolution equation for shear stress\ntensor is derived from its kinetic definition up-to third-order in gradients.\nWe quantify the significance of the new derivation within one-dimensional\nscaling expansion and demonstrate that the results obtained using third-order\nviscous equations derived here provides a very good approximation to the exact\nsolution of Boltzmann equation in relaxation time approximation. We also show\nthat the time evolution of pressure anisotropy obtained using our equations is\nin better agreement with transport results when compared with an existing\nthird-order calculation based on the second-law of thermodynamics.", "category": "nucl-th" }, { "text": "Photoproduction $\u03b3p \\to K^{*+} \u039b$ in a Reggeized model: The high-precision differential cross-section data for the reaction $\\gamma p\n\\to K^{*+}\\Lambda$ are reanalyzed within a Regge-inspired effective Lagrangian\napproach. The model adopts Regge phenomenology to constrain the $t$-channel\ncontributions from the $\\kappa$, $K$, and $K^*$ exchanges. A minimal number of\nresonances in the $s$ channel are introduced in constructing the reaction\namplitudes in order to describe the data. It is shown that the differential\ncross-section data for $\\gamma p \\to K^{*+}\\Lambda$ can be satisfactorily\ndescribed by introducing the only $N(2060){5/2}^-$ resonance in the $s$\nchannel, which is quite different from our earlier work performed in an\neffective Lagrangian approach [A. C. Wang {\\it et al.}, Phys. Rev. C 96, 035206\n(2017)], where the amplitudes are computed by evaluating Feynman diagrams and\nit is found that introducing at least one additional resonance apart from the\n$N(2060){5/2}^-$ is indispensable for reproducing the data. The roles of\nindividual contributions from meson and baryon exchanges on the angular\ndistributions are found to be highly model dependent. The extracted mass of\n$N(2060){5/2}^-$ turns out to be well determined, independent of how the\n$t$-channel amplitudes are constructed, whereas the width does not.", "category": "nucl-th" }, { "text": "`` $\u039b- \u03a3$ conversion in $^4_\u039b$He and $^4_\u039b$H\n based on four-body calculation: Precise four-body calculations for $^4_{\\Lambda}$He and $^4_{\\Lambda}$H have\nbeen performed in the framework of the variational method with\nJacobian-coordinate Gaussian-basis functions. All the rearrangement channels of\nboth $NNN \\Lambda$ and $NNN \\Sigma$ are explicitly taken into account for the\nfirst time with the use of realistic $NN$ and $YN$ interactions. The role of\n$\\Lambda$-$\\Sigma$ conversion and the amount of the virtual $\\Sigma$-component\nin $^4_{\\Lambda}$He and $^4_{\\Lambda}$H are discussed.", "category": "nucl-th" }, { "text": "Induced magnetic moment in the magnetic catalysis of chiral symmetry\n breaking: The chiral symmetry breaking in a Nambu-Jona-Lasinio effective model of\nquarks in the presence of a magnetic field is investigated. We show that new\ninteraction tensor channels open up via Fierz identities due to the explicit\nbreaking of the rotational symmetry by the magnetic field. We demonstrate that\nthe magnetic catalysis of chiral symmetry breaking leads to the generation of\ntwo independent condensates, the conventional chiral condensate and a spin-one\ncondensate. While the chiral condensate generates, as usual, a dynamical\nfermion mass, the new condensate enters as a dynamical anomalous magnetic\nmoment in the dispersion of the quasiparticles. Since the pair, formed by a\nquark and an antiquark with opposite spins, possesses a resultant magnetic\nmoment, an external magnetic field can align it giving rise to a net magnetic\nmoment for the ground state. The two condensates contribute to the effective\nmass of the LLL quasiparticles in such a way that the critical temperature for\nchiral symmetry restoration becomes enhanced.", "category": "nucl-th" }, { "text": "Generalized time-dependent generator coordinate method for small and\n large amplitude collective motion: An implementation of the generalized time-dependent generator coordinated\nmethod (TD-GCM) is developed, that can be applied to the dynamics of small- and\nlarge-amplitude collective motion of atomic nuclei. Both the generator states\nand weight functions of the GCM correlated wave function depend on time. The\ninitial generator states are obtained as solutions of deformation-constrained\nself-consistent mean-field equations, and are evolved in time by the standard\nmean-field equations of nuclear density functional theory (TD-DFT). The TD-DFT\ntrajectories are used as a generally non-orthogonal and overcomplete basis in\nwhich the TD-GCM wave function is expanded. The weights, expressed in terms of\na collective wave function, obey a TD-GCM (integral) equation. In this\nexplorative paper, the generalized TD-GCM is applied to the excitation energies\nand spreading width of giant resonances, and to the dynamics of induced\nfission. The necessity of including pairing correlations in the basis of TD-DFT\ntrajectories is demonstrated in the latter example.", "category": "nucl-th" }, { "text": "$\u03c0\u03c0$ scattering in the $\u03c1$-meson channel at finite temperature: We study $\\pi\\pi$ scattering in the I=1, $J^P=1^-$ channel at finite\ntemperature in the framework of the extended Nambu-Jona-Lasinio model that\nexplicitly includes vector and axial-vector degrees of freedom in addition to\nthe usual scalar and pseudoscalar sector. The S-matrix in the coupled channels\n$q\\bar q$ and $\\pi \\pi$ is constructed via $\\rho$-exchange in the $s$-channel.\nThe self-energy of the $\\rho$-meson contains both quark and pion loop\ncontributions. The analytic structure of the S-matrix for $T\\geq 0$ is\ninvestigated and the motion of the $\\rho$-pole as a function of coupling\nconstant and temperature is followed in the complex $\\sqrt{s}$-plane. For\nnumerical calculations, parameters are chosen in order that $m_\\pi$, $f_\\pi$\nand the experimental $\\pi\\pi$ phase shifts $\\delta_1^1$ at zero temperature are\nreproduced, and then the behavior of the $\\rho$-pole as well as the $\\pi\\pi$\ncross section is investigated as a function of the temperature. We find that\nthe position of the $\\rho$ mass stays practically constant for $0\\leq T\\leq\n130$ MeV, and then moves down in energy by about 200 MeV for 130 MeV$\\leq T\\leq\n230$ MeV.", "category": "nucl-th" }, { "text": "Partial dynamical symmetry in quantum Hamiltonians with higher-order\n terms: A generic procedure is proposed to construct many-body quantum Hamiltonians\nwith partial dynamical symmetry. It is based on a tensor decomposition of the\nHamiltonian and allows the construction of a hierarchy of interactions that\nhave selected classes of solvable states. The method is illustrated in the\nSO(6) limit of the interacting boson model of atomic nuclei and applied to the\nnucleus $^{196}$Pt.", "category": "nucl-th" }, { "text": "Wormhole Model for Neon-20: A quantum mechanical model for the Neon-20 nucleus is developed that allows\nfor the splitting of a bipyramidal structure of five alpha-partices into an\nalpha-particle and an Oxygen-16 nucleus. The geometry of the configuration\nspace is assumed to be a 3-dimensional spatial wormhole, and on the wormhole\nbackground there is an attractive short-range potential. This leads to a radial\nSchr\\\"odinger equation of the Heun form, which simplifies for threshold bound\nstates to an associated Legendre equation that has explicit solutions. The\nenergies of the true bound states for all spin/parities are numerically\ncalculated, and match those of the well-established $K^\\pi=0^+$, $K^\\pi=0^-$,\nand certain higher rotational bands of Neon-20.", "category": "nucl-th" }, { "text": "A simple functional form for proton-${}^{208}$Pb total reaction cross\n sections: A simple functional form has been found that gives a good representation of\nthe total reaction cross sections for the scattering from ${}^{208}$Pb of\nprotons with energies in the range 30 to 300 MeV.", "category": "nucl-th" }, { "text": "Determination of the $\\boldsymbol{\u03b7^3{\\rm He}}$ threshold structure\n from the low energy $\\boldsymbol{pd \\to \u03b7^3{\\rm He}}$ reaction: We analyze the data on cross sections and asymmetries for the $pd (dp) \\to\n\\eta ^3{\\rm He}$ reaction close to threshold and look for bound states of the\n$\\eta ^3 {\\rm He}$ system. Rather than parameterizing the scattering matrix, as\nis usually done, we develop a framework in which the $\\eta ^3 {\\rm He}$ optical\npotential is the key ingredient, and its strength, together with some\nproduction parameters, are fitted to the available experimental data. The\nrelationship of the scattering matrix to the optical potential is established\nusing the Bethe-Salpeter equation and the $\\eta ^3 {\\rm He}$ loop function\nincorporates the range of the interaction given by the empirical $^3 {\\rm He}$\ndensity. We find a local Breit Wigner form of the $\\eta^3$He amplitude $T$\nbelow threshold with a clear peak in $|T|^2$, which corresponds to an $\\eta^3\n{\\rm He}$ binding of about 0.3 MeV and a width of about 3 MeV. By fitting the\npotential we can also evaluate the $\\eta ^3 {\\rm He}$ scattering length,\nincluding its sign, thus resolving the ambiguity in the former analyses.", "category": "nucl-th" }, { "text": "Threshold 3He and 3H Transverse Electron Scattering Response Functions: The threshold transverse response functions R_T(q,omega) for 3He and 3H are\ncalculated using the AV18 nucleon-nucleon potential, the UrbanaIX three-body\nforce, and the Coulomb potential. Final states are completely taken into\naccount via the Lorentz integral transform technique. Consistent two-body pi-\nand rho-meson exchange currents as deduced using the Arenh\\\"ovel-Schwamb\ntechnique are included. The convergence of the method is shown and a comparison\nof the corresponding MEC contribution is made to that of a consistent MEC for\nthe meson theoretical r-space BonnA potential. The response R_T is calculated\nin the threshold region at q=174, 324, and 487 MeV/c and compared with\navailable data. The strong MEC contributions in the threshold region are nicely\nconfirmed by the data at q=324 and 487 MeV/c although some differences between\ntheoretical and experimental results remain. A comparison is also made with\nother calculations, where the same theoretical input is used. The agreement is\ngenerally rather good, but leaves also some space for further improvement.", "category": "nucl-th" }, { "text": "Measuring the speed of sound using cumulants of baryon number: We show that the values of the first three cumulants of the baryon number\ndistribution can be used to calculate the isothermal speed of sound and its\nlogarithmic derivative with respect to the baryon number density. We discuss\napplications of this result to heavy-ion collision experiments and address\npossible challenges, including effects due to baryon number conservation,\ndifferences between proton and baryon cumulants, and the influence of finite\nnumber statistics on fluctuation observables in both experiment and hadronic\ntransport simulations. In particular, we investigate the relation between\nquantities calculated in infinite, continuous matter and observables obtained\nin simulations using a finite number of particles.", "category": "nucl-th" }, { "text": "Decorrelation of anisotropic flows along the longitudinal direction: The initial energy density distribution and fluctuation in the transverse\ndirection lead to anisotropic flows of final hadrons through collective\nexpansion in high-energy heavy-ion collisions. Fluctuations along the\nlongitudinal direction, on the other hand, can result in decorrelation of\nanisotropic flows in different regions of pseudo rapidity ($\\eta$).\nDecorrelation of the $2$nd and $3$rd order anisotropic flows with different\n$\\eta$ gaps for final charged hadrons in high-energy heavy-ion collisions is\nstudied in an event-by-event (3+1)D ideal hydrodynamic model with fully\nfluctuating initial conditions from A Multi-Phase Transport (AMPT) model. The\ndecorrelation of anisotropic flows of final hadrons with large $\\eta$ gaps are\nfound to originate from the spatial decorrelation along the longitudinal\ndirection in the AMPT initial conditions through hydrodynamic evolution. The\ndecorrelation is found to consist of both a linear twist and random fluctuation\nof the event-plane angles. The agreement between our results and recent CMS\ndata in most centralities suggests that the string-like mechanism of initial\nparton production in AMPT model captures the initial longitudinal fluctuation\nthat is responsible for the measured decorrelation of anisotropic flows in\nPb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest\nRHIC energy show stronger longitudinal decorrelation, indicating larger\nlongitudinal fluctuations at lower beam energies. Our study also calls into\nquestion some of the current experimental methods for measuring anisotropic\nflows and extraction of transport coefficients through comparisons to\nhydrodynamic simulations that do not include longitudinal fluctuations.", "category": "nucl-th" }, { "text": "Probing nuclear quadrupole deformation from correlation of elliptic flow\n and transverse momentum in heavy ion collisions: In heavy ion collisions, elliptic flow $v_2$ and radial flow, characterized\nby event-wise average transverse momentum $[p_{\\mathrm{T}}]$, are related to\nthe shape and size of the overlap region, which are sensitive to the shape of\ncolliding atomic nuclei. The Pearson correlation coefficient between $v_2$ and\n$[p_{\\mathrm{T}}]$, $\\rho_2$, was found to be particularly sensitive to the\nquadrupole deformation parameter $\\beta$ that is traditionally measured in low\nenergy experiments. Built on earlier insight that the prolate deformation\n$\\beta>0$ reduces the $\\rho_2$ in ultra-central collisions (UCC), we show that\nthe prolate deformation $\\beta<0$ enhances the value of $\\rho_2$. As $\\beta>0$\nand $\\beta<0$ are the two extremes of triaxiality, the strength and sign of\n$v_2^2-[p_{\\mathrm{T}}]$ correlation can be used to provide valuable\ninformation on the triaxiality of the nucleus. Our study provide further\narguments for using the hydrodynamic flow as a precision tool to directly image\nthe deformation of the atomic nuclei at extremely short time scale\n($<10^{-24}$s).", "category": "nucl-th" }, { "text": "Recent developments in weak-coupling color superconductivity: Recent developments in weak-coupling color superconductivity are reviewed.\nThese developments are as follows. The mean field gap equation is solved for\nmost common superconducting phases up to subleading order; BCS relation is\nfound to be violated in color-flavor-locking and color-spin-locking phases due\nto the two-gaps structure of the order parameter; The Debye and Meissner masses\nof gluons and photon with their rotated partners are calculated for these\nphases; We found that there is no electromagnetic Meissner effect in spin-one\ncolor superconductor; A proof of gauge parameter independence at subleading\norder is given in covariant gauge.", "category": "nucl-th" } ]